Twain 2 1 Spec

TWAIN Specification

Version 2.1

This document was released for IP by the TWAIN Working Group on July 8, 2009

AcknowledgmentsThe TWAIN Working Group acknowledges the following individuals and their respective companies for their contributions to this document. Their hard work in defining, designing, editing, proofreading, and discussing the evolution of the document have been invaluable.

We would also like to thank the TWAIN Working Group Technical Committee for their opinions and contributions..

Adobe Systems IncorporatedScott Foshee

AnyDoc Software, Inc.Merit Greaves

AtalasoftGlenn Chittenden Jr.Adam Scarborough

Avision inc.Leo Liao

Eastman Kodak CompanyMark McLaughlin

EpsonTak Shiozaki

Fujitsu Computer Products of AmericaPamela Doyle

Hewlett-PackardYuri Breloff

JFL Peripheral Solutions Inc.Fred HarjuJon HarjuJim Watters

Ricoh Americas CorporationRob Pope

The TWAIN Working GroupHilary Minugh

Trees & GeneralsDebra Herman

XeroxWayne Buchar

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Need for Consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Elements of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1

Benefits of Using TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2

Creation of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

2. Technical Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

TWAIN Architecture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1

TWAIN User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3

Communication Between the Elements of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5

Using Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11

The State-Based Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13

Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16

Modes Available for Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

3. Application Implementation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Levels of TWAIN Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1

Installation of the Source Manager Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2

Changes Needed to Prepare for a TWAIN Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5

Controlling a TWAIN Session from Your Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15

Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39

Requirements for an Application to be TWAIN-Compliant . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

TWAIN 2.1 Specification i

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4. Advanced Application Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4-1

Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1

Options for Transferring Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17

The ImageData and Its Layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24

Transfer of Multiple Images . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27

Transfer of Compressed Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-33

Alternative User Interfaces . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37

Grayscale and Color Information for an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-40

Contrast, Brightness, and Shadow Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42

5. Source Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5-1

The Structure of a Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2

Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3

Sources and the Event Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4

User Interface Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7

Capability Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10

Data Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12

Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15

Memory Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17

Requirements for a Source to be TWAIN-Compliant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18

Other Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

6. Entry Points and Triplet Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6-1

Entry Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1

Data Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Data Argument Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4

Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6

Custom Components of Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

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7. Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Triplet Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1

Format of the Operation Triplet Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5

Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

8. Data Types and Data Structures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

Naming Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1

Platform Dependent Definitions and Typedefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3

Definitions of Common Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

Data Structure Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7

Data Argument Types that Don’t Have Associated TW_Structures . . . . . . . . . . . . . . . . . . . 8-63

Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-65

Deprecated Items . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-101

9. Extended Image Information Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

TWAIN 1.7 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1

TWAIN 1.9 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12

TWAIN 1.91 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16



10. Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1

Required Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

Capabilities in Categories of Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2

11. Return Codes and Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

An Overview of Return Codes and Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1

TWAIN 2.1 Specification iii

Table of Contents

Currently Defined Return Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

Currently Defined Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2

Custom Return and Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4

A. TWAIN Articles. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A 1

Device Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1

Supported Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-5

Automatic Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8

Camera Preview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-9

File System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-11

Internationalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-19

Audio Snippets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-19

How to use the Preview Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21

Imprinter / Endorser . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-23

Capability Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-24

Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

B. TWAIN Technical Support. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B 1

E-Mail Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1

Worldwide Web . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2

iv TWAIN 2.1 Specification

1Introduction

Chapter ContentsNeed for Consistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1Elements of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1Benefits of Using TWAIN. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-2Creation of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-3

Need for ConsistencyWith the introduction of scanners, digital cameras, and other image acquisition devices, users eagerly discovered the value of incorporating images into their documents and other work. However, supporting the display and manipulation of this raster data placed a high cost on application developers. They needed to create user interfaces and build in device control for the wide assortment of available image devices. Once their application was prepared to support a given device, they faced the discouraging reality that devices continue to be upgraded with new capabilities and features. Application developers found themselves continually revising their product to stay current.

Developers of both the image acquisition devices and the software applications recognized the need for a standard communication between the image devices and the applications. A standard would benefit both groups as well as the users of their products. It would allow the device vendors’ products to be accessed by more applications and application vendors could access data from those devices without concern for which type of device, or particular device, provided it. TWAIN was developed because of this need for consistency and simplification.

Elements of TWAINTWAIN defines a standard software protocol and API (application programming interface) for communication between software applications and image acquisition devices (the source of the data).

TWAIN 2.1 Specification 1-1

Chapter 1

The three key elements in TWAIN are:

• Application software An application must be modified to use TWAIN.

• Source Manager software This software manages the interactions between the application and the Source. This code is provided in the TWAIN Developer’s Toolkit and should be shipped for free with each TWAIN application and Source.

• Source softwareThis software controls the image acquisition device and is written by the device developer to comply with TWAIN specifications. Traditional device drivers are now included with the Source software and do not need to be shipped by applications.

Figure 1-1 TWAIN Elements

Benefits of Using TWAIN

For the Application Developer• Allows you to offer users of your application a simple way to incorporate images from any

compatible raster device without leaving your application.

• Saves time and dollars. If you currently provide low-level device drivers for scanners, etc., you no longer need to write, support, or ship these drivers. The TWAIN-compliant image acquisition devices will provide Source software modules that eliminate the need for you to create and ship device drivers.

• Permits your application to access data from any TWAIN-compliant image peripheral simply by modifying your application code once using the high-level TWAIN application programming interface. No customization by product is necessary. TWAIN image peripherals can include desktop scanners, hand scanners, digital cameras, frame grabbers,

ImageApplication

Data SourceManager

FaxApplication

Word ProcessorApplication

Digital CameraData Source

ScannerData Source

Image DatabaseData Source

Producers ofImage Data

Consumers ofImage Data

HW Dependant I/O Layer(SCSI, Parallel, Serial, etc.)

Source ManagerSoftware

Data SourceSoftware

ApplicationSoftware

TWAINInterfaces

1-2 TWAIN 2.1 Specification

image databases, or any other raster image source that complies to the TWAIN protocol and API.

• Allows you to determine the features and capabilities that an image acquisition device can provide. Your application can then restrict the Source to offer only those capabilities that are compatible with your application’s needs and abilities.

• Eliminates the need for your application to provide a user interface to control the image acquisition process. There is a software user interface module shipped with every TWAIN-compliant Source device to handle that process. Of course, you may provide your own user interface for acquisition, if desired.

For the Source Developer• Increases the use and support of your product. More applications will become image

consumers as a result of the ease of implementation and breadth of device integration that TWAIN provides.

• Allows you to provide a proprietary user interface for your device. This lets you present the newest features to the user without waiting for the applications to incorporate them into their interfaces.

• Saves money by reducing your implementation costs. Rather than create and support various versions of your device control software to integrate with various applications, you create just a single TWAIN-compliant Source.

For the End User• Gives users a simple way to incorporate images into their documents. They can access the

image in fewer steps because they never need to leave your application.

Note: As of this writing TWAIN is supported on the following operating systems: all versions of Apple Macintosh, Microsoft Windows 3.x / 9x / NT /Me /XP and Windows 2000. TWAIN is not available on Windows CE. TWAIN is available on IBM OS/2, but the binaries for the Source Manager were not built or distributed by the TWAIN Working Group.

Creation of TWAINTWAIN was created by a small group of software and hardware companies in response to the need for a proposed specification for the imaging industry. The Working Group’s goal was to provide an open, multi-platform solution to interconnect the needs of raster input devices with application software. The original Working Group was comprised of representatives from five companies: Aldus, Caere, Eastman Kodak, Hewlett-Packard, and Logitech. Three other companies, Adobe, Howtek, and Software Architects also contributed significantly.

The design of TWAIN began in January, 1991. Review of the original TWAIN Developer’s Toolkit occurred from April, 1991 through January, 1992. The original Toolkit was reviewed by the TWAIN Coalition. The Coalition includes approximately 300 individuals representing 200 companies who continue to influence and guide the future direction of TWAIN.


Chapter 1

The current version of TWAIN was written by members of the TWAIN Working Group including Adobe, Eastman Kodak Company, Fujitsu Computer Products of America, Hewlett-Packard Company, JFL Peripheral Solutions Inc., Ricoh Corporation, Xerox Corporation, and Lizardtech Corporation.

In May, 1998, an agreement was announced between Microsoft and the TWAIN Working Group which provided for the inclusion of the TWAIN Data Source Manager in Microsoft Windows 98 and Microsoft Windows NT 5.0.

During the creation of TWAIN, the following architecture objectives were adhered to:

• Ease of Adoption — Allow an application vendor to make their application TWAIN-compliant with a reasonable amount of development and testing effort. The basic features of TWAIN should be implemented just by making modest changes to the application. To take advantage of a more complete set of functionality and control capabilities, more development effort should be anticipated.

• Extensibility — The architecture must include the flexibility to embrace multiple windowing environments spanning various host platforms (Macintosh, Microsoft Windows, Motif, etc.) and facilitate the exchange of various data types between Source devices and destination applications. Currently, only the raster image data type is supported but suggestions for future extensions include text, facsimile, vector graphics, and others.

• Integration—Key elements of the TWAIN implementation “belong” in the operating system. The agreement between Microsoft and the TWAIN Working Group indicates that this integration into the operating system is beginning. TWAIN must be implemented to encourage backward compatibility (extensibility) and smooth migration into the operating system. An implementation that minimizes the use of platform-specific mechanisms will have enhanced longevity and adoptability.

• Easy Application <-> Source Interconnect— A straight-forward Source identification and selection mechanism will be supplied. The application will drive this mechanism through a simple API. This mechanism will also establish the data and control links between the application and Source. It will support capability and configuration communication and negotiation between the application and Source.

• Encapsulated Human Interface — A device-native user interface will be required in each Source. The application can optionally override this native user interface while still using the Source to control the physical device.


2Technical Overview

Chapter ContentsTWAIN Architecture. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-1TWAIN User Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-3Communication Between the Elements of TWAIN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-5Using Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-11The State-Based Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-13Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-16Modes Available for Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-21

The TWAIN protocol and API are easiest to understand when you see the overall picture. This chapter provides a technical overview of TWAIN.

TWAIN ArchitectureThe transfer of data is made possible by three software elements that work together in TWAIN: the application, the Source Manager, and the Source.

These elements use the architecture of TWAIN to communicate. The TWAIN architecture consists of four layers:

• Application

• Protocol

• Acquisition

• Device

The TWAIN software elements occupy the layers as illustrated below. Each layer is described in the sections that follow.


Chapter 2

Figure 2-1 TWAIN Software Elements

Application

The user’s software application executes in this layer.

TWAIN describes user interface guidelines for the application developer regarding how users access TWAIN functionality and how a particular Source is selected.

TWAIN is not concerned with how the application is implemented. TWAIN has no effect on any inter-application communication scheme that the application may use.

Protocol

The protocol is the “language” spoken and syntax used by TWAIN. It implements precise instructions and communications required for the transfer of data.

The protocol layer includes:

• The portion of application software that provides the interface between the application and TWAIN

• The TWAIN Source Manager provided by TWAIN

• The software included with the Source device to receive instructions from the Source Manager and transfer back data and Return Codes

The contents of the protocol layer are discussed in more detail in “Communication Between the Elements of TWAIN” on page 2-5“.


http://www.twain.org

Acquisition

Acquisition devices may be physical (like a scanner or digital camera) or logical (like an image database). The software elements written to control acquisitions are called Sources and reside primarily in this layer.

The Source transfers data for the application. It uses the format and transfer mechanism agreed upon by the Source and application.

The Source always provides a built-in user interface that controls the device(s) the Source was written to drive. An application can override this and present its own user interface for acquisition, if desired.

Device

This is the location of traditional low-level device drivers. They convert device-specific commands into hardware commands and actions specific to the particular device the driver was written to accompany. Applications that use TWAIN no longer need to ship device drivers because they are part of the Source.

TWAIN is not concerned with the device layer at all. The Source hides the device layer from the application. The Source provides the translation from TWAIN operations and interactions with the Source’s user interface into the equivalent commands for the device driver that cause the device to behave as desired.

Note: The Protocol layer is the most thoroughly and rigidly defined to allow precise communications between applications and Sources. The information in this document concentrates on the Protocol and Acquisition layers.

TWAIN User InterfaceWhen an application uses TWAIN to acquire data, the acquisition process may be visible to the application’s users in the following three areas:


Chapter 2

Figure 2-2 Data Acquisition Process

The Application

The user needs to select the device from which they intend to acquire the data. They also need to signal when they are ready to have the data transferred. To allow this, TWAIN strongly recommends the application developer add two options to their File menu:

• Select Source - to select the device

• Acquire - to begin the transfer process

The Source Manager

When the user chooses the Select Source option, the application requests that the Source Manager display its Select Source dialog box. This lists all available devices and allows the user to highlight and select one device. If desired, the application can write its own version of this user interface.

The Source

Every TWAIN-compliant Source provides a user interface specific to its particular device. When the application user selects the Acquire option, the Source’s User Interface may be displayed. If desired, the application can write its own version of this interface, too.


Communication Between the Elements of TWAINCommunication between elements of TWAIN is possible through two entry points. They are called DSM_Entry( ) and DS_Entry( ). DSM means Data Source Manager and DS means Data Source.

Figure 2-3 Entry Points for Communicating Between Elements

The Application

The goal of the application is to acquire data from a Source. However, applications cannot contact the Source directly. All requests for data, capability information, error information, etc. must be handled through the Source Manager.

Approximately 140 operations are defined by TWAIN. The application sends them to the Source Manager for transmission. The application specifies which element, Source Manager or Source, is the final destination for each requested operation.

The application communicates to the Source Manager through the Source Manager’s only entry point, the DSM_Entry( ) function.

The parameter list of the DSM_Entry function contains:

• An identifier structure providing information about the application that originated the function call

• The destination of this request (Source Manager or Source)

• A triplet that describes the requested operation. The triplet specifies:

• Data Group for the Operation (DG_ )

• Data Argument Type for the Operation (DAT_ )

• Message for the Operation (MSG_ )


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• (These are described more in the section called “The Use of Operation Triplets” located later in this chapter.)

• A pointer field to allow the transfer of data

The function call returns a value (the Return Code) indicating the success or failure of the operation.

Written in C code form, the function call looks like this:

On Windows

TW_UINT16 FAR PASCAL DSM_Entry ( pTW_IDENTITY pOrigin, // source of message

pTW_IDENTITY pDest, // destination of messageTW_UINT32 DG, // data group ID: DG_xxxxTW_UINT16 DAT, // data argument type: DAT_xxxxTW_UINT16 MSG, // message ID: MSG_xxxxTW_MEMREF pData // pointer to data

);

On Macintosh

FAR PASCAL TW_UINT16 DSM_Entry ( pTW_IDENTITY pOrigin, // source of message

pTW_IDENTITY pDest, // destination of messageTW_UINT32 DG, // data group ID: DG_xxxxTW_UINT16 DAT, // data argument type: DAT_xxxxTW_UINT16 MSG, // message ID: MSG_xxxxW_MEMREF pData // pointer to data

);

Note: Data type definitions are covered in Chapter 8, "Data Types and Data Structures,” and in the file called TWAIN.H which can be downloaded from the TWAIN Working Group web site http://www.twain.org.)

The Source Manager

The Source Manager provides the communication path between the application and the Source, supports the user’s selection of a Source, and loads the Source for access by the application. Communications from application to Source Manager arrive in the DSM_Entry( ) entry point.

• If the destination in the DSM_Entry call is the Source Manager The Source Manager processes the operation itself.

• If the destination in the DSM_Entry call is the SourceThe Source Manager translates the parameter list of information, removes the destination parameter and calls the appropriate Source. To reach the Source, the Source Manager calls the Source’s DS_Entry( ) function. TWAIN requires each Source to have this entry point.

Written in C code form, the DS_Entry function call looks like this:


On Windows

TW_UINT16 FAR PASCAL DS_Entry (pTW_IDENTITY pOrigin, // source of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

On Macintosh

FAR PASCAL TW_UINT16 DS_Entry (pTW_IDENTITY pOrigin, // source of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

In addition, the Source Manager can initiate three operations that were not originated by the application. These operation triplets exist just for Source Manager to Source communications and are executed by the Source Manager while it is displaying its Select Source dialog box. The operations are used to identify the available Sources and to open or close Sources.

The implementation of the Source Manager differs between the supported systems:

On Windows

• The Source Manager for Windows is a Dynamic Link Library (DLL).

• The Source Manager can manage simultaneous sessions between many applications with many Sources. That is, the same instance of the Source Manager is shared by multiple applications.

On Macintosh

• The Source Manager for Macintosh is a Mach-O framework (TWAIN.framework).

The Source

The Source receives operations either from the application, via the Source Manager, or directly from the Source Manager. It processes the request and returns the appropriate Return Code (the codes are prefixed with TWRC_) indicating the results of the operation to the Source Manager. If the originator of the operation was the application, then the Return Code is passed back to the application as the return value of its DSM_Entry( ) function call. If the operation was unsuccessful, a Condition Code (the codes are prefixed with TWCC_) containing more specific information is set by the Source. Although the Condition Code is set, it is not automatically passed back. The application must invoke an operation to inquire about the contents of the Condition Code.

The implementation of the Source is the same as the implementation of the Source Manager:


Chapter 2

On Windows

The Source is a Dynamic Link Library (DLL) so applications share the same copy of each element.

On Macintosh

The Source is implemented as a bundle (preferably Mach-O).

Communication Flowing from Source to Application

The majority of operation requests are initiated by the application and flow to the Source Manager and Source. The Source, via the Source Manager, is able to pass back data and Return Codes.

However, there are four times when the Source needs to interrupt the application and request that an action occur. These situations are:

• Notify the application that a data transfer is ready to occur. The time required for a Source to prepare data for a transfer will vary. Rather than have the application wait for the preparation to be complete, the Source just notifies it when everything is ready. The MSG_XFERREADY notice is used for this purpose.

• Request that the Source’s user interface be disabled. This notification should be sent by the Source to the application when the user clicks on the “Close” button of the Source’s user interface. The MSG_CLOSEDSREQ notice is used for this purpose.

• Notify the application that the OK button has been pressed, accepting the changes the user has made. This is only used if the Source is opened with DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDSUIONLY. The MSG_CLOSEDSOK notice is used for this purpose.

• A Device Event has occurred. This notification is sent by the Source to the Application when a specific event has occurred, but only if the Application gave the Source prior instructions to pass along such events. The MSG_DEVICEEVENT notice is used for this purpose.

These notices are presented to the application in its event (or message) loop. The process used for these notifications is covered more fully in Chapter 3, "Application Implementation,” in the discussion of the application’s event loop.

Identifying TWAIN 2.0 Elements

It is not sufficient to test the TW_IDENTITY.ProtocolMajor field to determine if an Application, a Data Source Manager or a Source is TWAIN 2.0 compliant. Check the TW_IDENTITY.SupportedGroups field for the Application or the Source, and look for the following:

• DF_APP2, indicating that the Application is 2.0 compliant

• DF_DSM2, indicating that the Data Source Manager is 2.0 compliant

• DF_DS2, indicating that the Data Source is 2.0 compliant


Applications

All TWAIN 2.0 compliant Applications must report DF_APP2 in their TW_IDENTITY.SupportedGroups field.

All TWAIN 2.0 compliant Applications must test for the DF_DSM2 flag in the TW_IDENTITY.SupportedGroups field, after a call to DG_CONTROL / DAT_PARENT / MSG_OPENDSM. If this flag is not found, then follow the legacy behavior for 1.x Applications, using the memory management functions detailed in the TWAIN Specification.

If the flag is found, then the Application must call DG_CONTROL / DAT_ENTRYPOINT / MSG_GET in State 3, before performing any other operation, to obtain pointers to the memory management functions.

Sources

All TWAIN 2.0 compliant Sources must report DF_DS2 in their TW_IDENTITY.SupportedGroups field.

All TWAIN 2.0 compliant Sources must be prepared to receive the DG_CONTROL / DAT_ENTRYPOINT / MSG_SET call in State 3, before DG_CONTROL / DAT_IDENTITY / MSG_OPENDS is called. If this operation is not called, then follow the legacy behavior for 1.x Sources, using the memory management functions detailed in the TWAIN Specification, and locating the Data Source Manager as indicated.

If the operation is called then the Source must use the pointers to the memory management functions, and must use the supplied entry point to access DSM_Entry.

Using DAT_CALLBACK to Messages from the Source to the Application

Applications

TWAIN Applications running on Linux or Apple Macintosh OS X must use DG_CONTROL / DAT_CALLBACK / MSG_REGISTERCALLBACK to register to receive asynchronous notifications for events MSG_XFERREADY.

TWAIN Applications on Microsoft Windows that detect the presence of the DF_DSM2 flag inside of TW_IDENTITY.SupportedGroups are encouraged to use DAT_CALLBACK instead of processing TWRC_DSEVENT from DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT. The legacy TWAIN 1.x behavior is still supported by the Data Source Manager.

TWAIN Applications on Microsoft Windows using older versions of the Data Source Manager (no DF_DSM2 flag detected) must use the legacy behavior.

Please note that TWAIN Applications are advised to return as soon as possible from a callback function. Events like MSG_XFERREADY should initiate the image transfer in a different thread so that the callback can return immediately.

Sources

TWAIN sources running on Apple Macintosh OS X that use a Data Source Manager that does not report DF_DSM2 in TW_IDENTITY.SupportedGroups must use DG_CONTROL / DAT_CALLBACK / MSG_INVOKECALLBACK to return events like MSG_XFERREADY.


Chapter 2

All other TWAIN sources, regardless of version or operating system must use DG_CONTROL / DAT_NULL with the appropriate message to return events like MSG_XFERREADY.

Installation of the Data Source Manager

Microsoft Windows

Please refer to the TWAIN 1.9 Specification for support of versions of Microsoft Windows prior to Windows 2000.

Microsoft provides TWAIN_32.DLL for access to the legacy 1.x Data Source Manager on 32-bit systems and SYSWOW64.

TWAIN_32.DLL is not available for native 64-bit Applications. A native 64-bit TWAIN session must use TWAINDSM.DLL.

Applications that wish to use TWAINDSM.DLL, for access to the new open source Data Source Manager, must install it themselves. Please refer to the TWAIN website http://www.twain.org to obtain this file, and for installation instructions. This DSM is fully backwards compatible with all versions of TWAIN.

Apple Macintosh

Please refer to the TWAIN 1.9 Specification for support of operating systems prior to Apple Mac OS X.

Apple provides /System/Library/Frameworks/TWAIN.framework for access to the legacy 1.x Data Source Manager.

The TWAIN 2.0 open source Data Source Manager is not currently available on any version of Apple Mac OS X. TWAIN 2.0 compliant Application and Source writers are strongly encouraged to include and check for the DF_APP2, DF_DSM2 and DF_DS2 flags, and to handle DAT_CALLBACK when these flags are detected, so they are ready when the TWAIN 2.0 Data Source Manager appears.

Linux

Please check the TWAIN website http://www.twain.org to see if your distro is represented, and if not, please consider making a submission to the TWAIN Working Group.

Note that TWAIN 2.0 compliant Sources must support TW_USERINTERFACE.ShowUI being set to 0 (no UI), which in concert with CAP_INDICATORS set to FALSE is expected to prevent the Source from showing any dialog, making it suitable for use from any command shell.

Memory Management in TWAIN 2.0 and Higher

TWAIN requires Applications and Sources to manage each other’s memory. The chief problem is guaranteeing agreement on the API’s to use.

TWAIN 2.0 introduces four new functions that are obtained from the Source Manager through DAT_ENTRYPOINT.

TW_HANDLE PASCAL DSM_MemAllocate (TW_UINT32)




void PASCAL DSM_MemFree (TW_HANDLE)

TW_MEMREF PASCAL DSM_MemLock (TW_HANDLE)

void PASCAL DSM_MemUnlock (TW_HANDLE)

This applies when a 1.x Application or Source is detected.

These functions correspond to the WIN32 Global Memory functions mentioned in previous versions of the TWAIN Specification:

GlobalAlloc, GlobalFree, GlobalLock, GlobalUnlock

On MacOS/X these functions call NewPtrClear and DisposePtr. The lock and unlock functions are no-ops, but they still must be called.

TWAIN 2.0 compliant Applications and Sources must use these calls on all platforms (Windows, MacOS/X and Linux).

The Source Manager takes the responsibility to make sure that all components are using the same memory management API’s.

Using Operation TripletsThe DSM_Entry( ) and DS_Entry( ) functions are used to communicate operations. An operation is an action that the application or Source Manager invokes. Typically, but not always, it involves using data or modifying data that is indicated by the last parameter (pData) in the function call.

Requests for actions occur in one of these ways:

The desired action is defined by an operation triplet passed as three parameters in the function call. Each triplet uniquely, and without ambiguity, specifies a particular action. No operation is specified by more than a single triplet. The three parameters that make up the triplet are Data Group, Data Argument Type, and Message ID. Each parameter conveys specific information.

From To Using this function

The application The Source Manager DSM_Entry with the pDest parameter set to NULL

The application The Source (via the Source Manager)

DSM_Entry with the pDest parameter set to point to a valid structure that identifies the Source

The Source Manager The Source DS_Entry


Chapter 2

Data Group (DG_xxxx)

Operations are divided into large categories by the Data Group identifier. There are currently only two defined in TWAIN:

• CONTROL (The identifier is DG_CONTROL.): These operations involve control of the TWAIN session. An example where DG_CONTROL is used as the Data Group identifier is the operation to open the Source Manager.

• IMAGE (The identifier is DG_IMAGE.): These operations work with image data. An example where DG_IMAGE is used as a Data Group is an operation that requests the transfer of image data.

• AUDIO (The identifier is DG_AUDIO): These operations work with audio data (supported by some digital cameras). An example where DG_AUDIO is used as a Data Group is an operation that requests the transfer of audio data.

Data Argument Type (DAT_xxxx)

This parameter of the triplet identifies the type of data that is being passed or operated upon. The argument type may reference a data structure or a variable. There are many data argument types. One example is DAT_IDENTITY. The DAT_IDENTITY type is used to identify a TWAIN element such as a Source. Remember, from the earlier code example, data is typically passed or modified through the pData parameter of the DSM_Entry and DSM_Entry. In this case, the pData parameter would point to a data structure of type TW_IDENTITY. Notice that the data argument type begins with DAT_xxxx and the associated data structure begins with TW_xxxx and duplicates the second part of the name. This pattern is followed consistently for most data argument types and their data structures. Any exceptions are noted on the reference pages in Chapter 7, "Operation Triplets” and Chapter 8, "Data Types and Data Structures.”

Message ID (MSG_xxxx)

This parameter identifies the action that the application or Source Manager wishes to have taken. There are many different messages such as MSG_GET or MSG_SET. They all begin with the prefix of MSG_.Here are three examples of operation triplets:

• The triplet the application sends to the Source Manager to open the Source Manager module is:

DG_CONTROL / DAT_PARENT / MSG_OPENDSM

• The triplet that the application sends to instruct the Source Manager to display its Select Source dialog box and thus allow the user to select which Source they plan to obtain data from is:

DG_CONTROL / DAT_IDENTITY / MSG_USERSELECT

• The triplet the application sends to transfer data from the Source into a file is:

DG_IMAGE / DAT_IMAGEFILEXFER / MSG_GET


The State-Based ProtocolThe application, Source Manager, and Source must communicate to manage the acquisition of data. It is logical that this process must occur in a particular sequence. For example, the application cannot successfully request the transfer of data from a Source before the Source Manager is loaded and prepared to communicate the request.

To ensure the sequence is executed correctly, the TWAIN protocol defines seven states that exist in TWAIN sessions. A session is the period while an application is connected to a particular Source via the Source Manager. The period while the application is connected to the Source Manager is another unique session. At a given point in a session, the TWAIN elements of Source Manager and Source each occupy a particular state. Transitions to a new state are caused by operations requested by the application or Source. Transitions can be in the forward or backward direction. Most transitions are single-state transitions. For example, an operation moves the Source Manager from State 1 to State 2 not from State 1 to State 3. (There are situations where a two-state transition may occur. They are discussed in Chapter 3, "Application Implementation.”)

When viewing the state-based protocol, it is helpful to remember:

States 1, 2, and 3

• Are occupied only by the Source Manager.

• The Source Manager never occupies a state greater than State 3.

States 4, 5, 6, and 7

• Are occupied exclusively by Sources.

• A Source never has a state less than 4 if it is open. If it is closed, it has no state.

• If an application uses multiple Sources, each connection is a separate session and each open Source “resides” in its own state without regard for what state the other Sources are in.

The State Transition Diagram looks like this:


Chapter 2

Figure 2-4 State Transition Diagram

The Description of the States

The following sections describe the states.

State 1 — Pre-Session

The Source Manager resides in State 1 before the application establishes a session with it.At this point, the Source Manager code has been installed on the disk but typically is not loaded into memory yet.The only case where the Source Manager could already be loaded and running is under Windows because the implementation is a DLL (hence, the same instance of the Source

1Pre-Session

Source Manager notloaded

2Source Manager

LoadedApp: Get Entry Point

3Source Manager

OpenedUser: Select Source

App: LoadSource Manager

App: OpenSource Manager

App: Unload SourceManager

App: Close SourceManager

App: Open Source

Source: Transitionwhen no more imagetransfers are pending

Source: Notify Appto Disable Source.App: Disable Source

App: Initiatetransfer

Source: Notify Appthat transfer is ready

User: AcquireApp: Enable Source

App: Acknowledgeend of transfer

4Source Open

Capability Negotiation

5Source EnabledSource: Show User

Interface

6Transfer ReadyApp: Inquire Image

Information or AudioInformation

7Transferring

Source: Transfer Data

App: Close Source

Source Manager States Source States


Manager can be shared by multiple applications). If that situation exists, the Source Manager will be in State 2 or 3 with the application that loaded it.

State 2 — Source Manager Loaded

The Source Manager now is loaded into memory. It is not open yet.At this time, the Source Manager is prepared to accept other operation triplets from the application.

State 3 — Source Manager Open

The Source Manager is open and ready to manage Sources.The Source Manager is now prepared to provide lists of Sources, to open Sources, and to close Sources.The Source Manager will remain in State 3 for the remainder of the session until it is closed. The Source Manager refuses to be closed while the application has any Sources open.

State 4 — Source Open

The Source has been loaded and opened by the Source Manager in response to an operation from the application. It is ready to receive operations.The Source should have verified that sufficient resources (i.e. memory, device is available, etc.) exist for it to run.The application can inquire about the Source’s capabilities (i.e. levels of resolution, support of color or black and white images, automatic document feeder available, etc.). The application can also set those capabilities to its desired settings. For example, it may restrict a Source capable of providing color images to transferring black and white only.

Note: Inquiry about a capability can occur while the Source is in States 4, 5, 6, or 7. But, an application can set a capability only in State 4 unless special permission is negotiated between the application and Source.

State 5 — Source Enabled

The Source has been enabled by an operation from the application via the Source Manager and is ready for user-enabled transfers.If the application has allowed the Source to display its user interface, the Source will do that when it enters State 5.

State 6 — Transfer is Ready

The Source is ready to transfer one or more data items (images) to the application. The transition from State 5 to 6 is triggered by the Source notifying the application that the transfer is ready.Before initiating the transfer, the application must inquire information about the image (resolution, image size, etc.). If the Source supports audio, then before transferring the image, the Application must transfer all the audio snippets that are associated with the image.It is possible for more than one image to be transferred in succession. This topic is covered thoroughly inChapter 4, "Advanced Application Implementation.”


Chapter 2

State 7 — Transferring

The Source is transferring the image to the application.The transfer mechanism being used was negotiated during State 4. The transfer will either complete successfully or terminate prematurely. The Source sends the appropriate Return Code indicating the outcome.Once the Source indicates that the transfer is complete, the application must acknowledge the end of the transfer.

A TWAIN 2.0 compliant Application tests its TW_IDENTITY .SupportedGroups for DF_DSM2 after a call to DG_CONTROL/DAT_PARENT/MSG_OPENDSM and if found it issues a call to DG_CONTROL / DAT_ENTRYPOINT / MSG_GET.

A TWAIN 2.0 compliant Source is sent DG_CONTROL / DAT_ENTRYPOINT / MSG_SET; it tests the Application’s TW_IDENTITY.SupportedGroups for DF_DSM2 and DF_APP2.

CapabilitiesOne of TWAIN’s benefits is it allows applications to easily interact with a variety of acquisition devices. Devices can provide image or audio data. For instance,

• Some devices have automatic document feeders.

• Some devices are not limited to one image but can transfer multiple images.

• Some devices support color images.

• Some devices offer a variety of halftone patterns.

• Some devices support a range of resolutions while others may offer different choices.

• Some devices allow the recording of audio data associated with an image.

Developers of applications need to be aware of a Source’s capabilities and may influence the capabilities that the Source offers to the application’s users. To do this, the application can perform capability negotiation. The application generally follows this process:

• Determine if the selected Source supports a particular capability.

• Inquire about the Current Value for this capability. Also, inquire about the capability’s Default Value and the set of Available Values that are supported by the Source for that capability.

• Request that the Source set the Current Value to the application’s desired value. The Current Value will be displayed as the current selection in the Source’s user interface.

• Limit, if needed, the Source’s Available Values to a subset of what would normally be offered. For instance, if the application wants only black and white data, it can restrict the Source to transmit only that. If a limitation effects the Source’s user interface, the Source should modify the interface to reflect those changes. For example, it may gray out options that are not available because of the application’s restrictions.

• Verify that the new values have been accepted by the Source.


TWAIN capabilities are divided into three groups:

• CAP_xxxx: Capabilities whose names begin with CAP are capabilities that could apply to any general Source. Such capabilities include use of automatic document feeders, identification of the creator of the data, etc.

• ICAP_xxxx: Capabilities whose names begin with ICAP are capabilities that apply to image devices. The “I” stands for image. (When TWAIN is expanded to support other data transfer such as text or fax data, there will be TCAPs and FCAPs in a similar style.)

• ACAP_xxxx: Capabilities whose names begin with ACAP are capabilities that apply to devices that support audio. The “A” stands for audio.

Capability Containers

Capabilities exist in many varieties but all have a Default Value, Current Value, and may have other values available that can be supported if selected. To help categorize the supported values into clear structures, TWAIN defines four types of containers for capabilities.

In general, most capabilities can have more than one of these containers applied to them depending on how the particular Source implements the capability. The data structure for each of these containers is defined in Chapter 8, "Data Types and Data Structures.” A complete table with all defined capabilities is located in Chapter 10, "Capabilities.” A few of the capabilities must be supported by the application and Source. The remainder of the capabilities are optional.

Name of the Data Structure for the Container

Type of Contents

TW_ONEVALUE A single value whose current and default values are coincident. The range of available values for this type of capability is simply this single value. For example, a capability that indicates the presence of a document feeder could be of this type.

TW_ARRAY A rectangular array of values that describe a logical item. It is similar to the TW_ONEVALUE because the current and default values are the same and there are no other values to select from. For example, a list of the names, such as the supported capabilities list returned by the CAP_SUPPORTEDCAPS capability, would use this type of container.

TW_RANGE Many capabilities allow users to select their current value from a range of regularly spaced values. The capability can specify the minimum and maximum acceptable values and the incremental step size between values. For example, resolution might be supported from 100 to 600 in steps of 50 (100, 150, 200, ..., 550, 600).

TW_ENUMERATION This is the most general type because it defines a list of values from which the Current Value can be chosen. The values do not progress uniformly through a range and there is not a consistent step size between the values. For example, if a Source’s resolution options did not occur in even step sizes then an enumeration would be used (for example, 150, 400, and 600).


Chapter 2

Capability Negotiation and Container Types

It is very important for Application and Data Source developers to note that Container types are dictated by the Data Source in all cases where a value is queried. Also the allowable container types of each capability are clearly defined in Chapter 10, "Capabilities,” of the TWAIN Specification. The only time it is appropriate for the calling Application to specify a container type is during the MSG_SET operation. At that time, the Application must also consider the allowable containers and types for the particular capability.

Capability Containers and String Values

The only containers that can possibly hold a string are the following:

TW_ENUMERATION

TW_ARRAY

TW_ONEVALUE

It is not possible or useful to use this type in a TW_RANGE. in fact there is no case where a capability has been defined in Chapter 10, "Capabilities,” of the TWAIN Specification where a TW_RANGE is allowed for a TW_STRxxxx type of value.

There are four types of TWAIN strings defined for developer use:

TW_STR32

TW_STR64

TW_STR128

TW_STR256

As of version 1.7, only the following capabilities accept strings:

CAP_AUTHOR, TW_ONEVALUE, TW_STR128

CAP_CAPTION, TW_ONEVALUE, TW_STR255

CAP_TIMEDATE, TW_ONEVALUE, TW_STR32

ICAP_HALFTONES, TW_ONEVALUE/TW_ENUMERATION/TW_ARRAY, TW_STR32

The definition of the various container types could be confusing. For example, the definition of a TW_ONEVALUE is as follows:

/* TWON_ONEVALUE. Container for one value. */

typedef struct {

TW_UINT16 ItemType;

TW_UINT32 Item;

} TW_ONEVALUE, FAR * pTW_ONEVALUE;

At first glance, it is tempting to try placing the string into this container by assigning “Item” to be a pointer. This is not at all consistent with the implementation of other structures in the specification and introduces a host of problems concerning management of the memory occupied by the string. (See TW_IDENTITY for consistent TWAIN string use)


The correct and consistent method of holding a string in a TWAIN container is to ensure the string is embedded in the container itself. Either a new structure is defined within the developers code, or the added size is considered when allocating the container.

The following examples are designed to demonstrate possible methods of using TWAIN Strings in Containers. These examples are suitable for demonstration only, and require refinement to be put to real use.

Example 1:

TW_ONEVALUE structure defined for holding a TW_STR32 value

/* TWON_ONEVALUESTR32. Container for one value holding TW_STR32. */typedef struct { TW_UINT16 ItemType; TW_STR32 Item;} TW_ONEVALUESTR32, FAR * pTW_ONEVALUESTR32;

Note: Pay attention to two-byte structure packing when defining custom container structures.

This clearly demonstrates where the memory is allocated and where the string resides. The data source does not have to be concerned with how the string is managed locally, and the application does not have to be concerned with managing the string memory or contents.

Example 2:

TW_ONEVALUE structure allocated and filled with consideration of holding a TW_STR32 value (Windows Example)

HGLOBAL AllocateAndFillOneValueStr32( const pTW_STR32 pInString ){

DWORD dwContainerSize = 0l;HGLOBAL hContainer = NULL;pTW_ONEVALUE pOneValue = NULL;pTW_STR32 pString = NULL;assert(pInString);

// Note: This calculation will yield a size approximately one // pointer larger than that required for this container // (sizeof(TW_UINT32)). For simplicity the size difference// is negligible. The first TW_STR32 item shall be located// immediately after the pEnum->DefaultIndex member.

dwContainerSize = sizeof(TW_ONEVALUE) + sizeof(TW_STR32);hContainer = GlobalAlloc( GPTR, dwContainerSize );

if(hContainer){

pOneValue = (pTW_ONEVALUE)GlobalLock(hContainer);if(pOneValue){


Chapter 2

pOneValue->ItemType = TWTY_STR32; pString = (pTW_STR32)&pOneValue->Item; memcpy(pString, pInString, sizeof(TW_STR32)); GlobalUnlock(hContainer); pOneValue = NULL; pString = NULL;

}

}

return hContainer;}

Example 3:

TW_ENUMERATION structure allocated with consideration of holding TW_STR32 values (Windows Example)

HGLOBAL AllocateEnumerationStr32( TW_UINT32 unNumItems ){

DWORD dwContainerSize = 0l;HGLOBAL hContainer = NULL;pTW_ENUMERATION pEnum = NULL;

// Note: This calculation will yield a size approximately // one pointer larger than that required for this container// (sizeof(pTW_UINT8)). For simplicity the size difference is// negligible. The first TW_STR32 item shall be located// immediately after the pEnum->DefaultIndex member.dwContainerSize = sizeof(TW_ENUMERATION) + ( sizeof(TW_STR32) * unNumItems);hContainer = GlobalAlloc( GPTR, dwContainerSize );

if(hContainer){ pEnum = (pTW_ENUMERATION) GlobalLock(hContainer); if(pEnum) { pEnum->ItemType = TWTY_STR32; pEnum->NumItems = unNumItems;

GlobalUnlock(hContainer); pEnum = NULL; }}return hContainer;

}

Example 4

Indexing a string from an Enumeration Container

pTW_STR128 IndexStr128FromEnumeration( pTW_ENUMERATION pEnum, TW_UINT32 unIndex)


{ BYTE *pBegin = (BYTE *)&pEnum->ItemList[0]; assert(pEnum->NumItems > unIndex); assert(pEnum->ItemType == TWTY_STR128); pBegin += (unIndex * sizeof(TW_STR128)); return (pTW_STR128)pBegin;

}

Modes Available for Data TransferThere are three different modes that can be used to transfer data from the Source to the application: native, disk file, and buffered memory.

Note: At this time, TWAIN support for audio only allows native and disk file transfers.)

Native

Every Source must support this transfer mode. It is the default mode and is the easiest for an application to implement. However, it is restrictive (i.e. limited to the DIB or PICT formats and limited by available memory).

The format of the data is platform-specific:

• Windows: DIB (Device-Independent Bitmap)

• Macintosh: A handle to a Picture

The Source allocates a single block of memory and writes the image data into the block. It passes a pointer to the application indicating the memory location. The application is responsible for freeing the memory after the transfer.

Disk File

A Source is not required to support this transfer mode but it is recommended.

The application creates the file to be used in the transfer and ensures that it is accessible by the Source for reading and writing.

A capability exists that allows the application to determine which file formats the Source supports. The application can then specify the file format and file name to be used in the transfer.

The disk file mode is ideal when transferring large images that might encounter memory limitations with Native mode. Disk File mode is simpler to implement than the buffered mode discussed next. However, Disk File mode is a bit slower than Buffered Memory mode and the application must be able to manage the file after creation.


Chapter 2

Buffered Memory

Every Source must support this transfer mode.

The transfer occurs through memory using one or more buffers. Memory for the buffers are allocated and deallocated by the application.

The data is transferred as an unformatted bitmap. The application must use information available during the transfer (TW_IMAGEINFO and TW_IMAGEMEMXFER) to learn about each individual buffer and be able to correctly interpret the bitmap.

If using the Native or Disk File transfer modes, the transfer is completed in one action. With the Buffered Memory mode, the application may need to loop repeatedly to obtain more than one buffer of data.

Buffered Memory transfer offers the greatest flexibility, both in data capture and control. However, it is the least simple to implement.


3Application Implementation

Chapter ContentsLevels of TWAIN Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-1Installation of the Source Manager Software. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-2Changes Needed to Prepare for a TWAIN Session . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-5Controlling a TWAIN Session from Your Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-15Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-39Requirements for an Application to be TWAIN-Compliant . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-41

This chapter provides the basic information needed to implement TWAIN at a minimum level.

Mac OS X includes two high-level native development environments that you can use for your application’s graphical user interface: Carbon, and Cocoa. These environments are full-featured development environments in their own right, and you can write TWAIN applications and TWAIN Data Sources in any one of these environments.

Because both Carbon and Cocoa change the event handling mechanism (no WaitNextEvent loops), these paragraphs update and extend the section of the previous specification that describes how to modify the application event loop to support TWAIN.

Carbon and Cocoa-based Mac OS X TWAIN applications are required to supply an event handler callback function that the TWAIN DSM will call. Carbon applications using the Classic Event Manager (WaitNextEvent)should continue to route all events through the Data Source of the Specification. However, Data Sources on Mac OS X can no longer use the Classic Event Manager.

Advanced topics are discussed in Chapter 4, "Advanced Application Implementation.” They include how to take advantage of Sources that offer automatic feeding of multiple images.

Levels of TWAIN ImplementationApplication developers can choose to implement TWAIN features in their application along a range of levels.


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• At the minimum level: The application does not have to take advantage of capability negotiation or transfer mode selection. Using TWAIN defaults, it can just acquire a single image in the Native mode.

• At a greater level: The application can negotiate with the Source for desired capabilities or image characteristics and specify the transfer arrangement. This gives the application more control over the type of image it receives. To do this, developers should follow the instructions provided in this chapter and use information from Chapter 4, "Advanced Application Implementation,” as well.

• At the highest level: An application may choose to negotiate capabilities, select transfer mode, and create/present its own user interfaces instead of using the built-in ones provided with the Source Manager and Source. Again, refer to this chapter and Chapter 4, "Advanced Application Implementation.”

Installation of the Source Manager SoftwareThe TWAIN Source Manager for Microsoft Windows consists of four binaries that are owned by the TWAIN Working Group (TWG). These binaries are built and distributed by the TWG for Windows 3.x / 9x / NT, and built and distributed by Microsoft (as protected system files) for all versions of Windows 2000. These files are as follows:

TWAIN_32.DLL The 32-bit Source Manager. This is the DLL that 32-bit applications must use to communicate with TWAIN.

TWAIN.DLL The 16-bit Source Manager. This is the DLL that 16-bit applications must use to communicate with TWAIN.

TWUNK_32.EXE This program works invisibly under the hood to allow 16-bit applications to communicate with 32-bit Sources.

TWUNK_16.EXE This program works invisibly under the hood to allow 32-bit applications to communicate with 16-bit Sources. Note that 16-bit Sources will not run correctly on Windows NT systems.

For a TWAIN-compliant application or Source to work properly, a Source Manager must be installed on the host system. To guarantee that a Source Manager is available, ship a copy of the latest Source Manager on your product’s distribution disk and provide the user with an installer or installation instructions as suggested below. To ensure that the most recent version of the Source Manager is available to you and your user on their computer, you must do the following:

1. Look for a Source Manager:On Windows systems: Look for the file names TWAIN.DLL, TWAIN_32.DLL, TWUNK_16.EXE, and TWUNK_32.EXE in the Windows directory (this is typically C:\Windows on Windows 3.1/95/98, and C:\Winnt on Windows NT).On Macintosh systems: There’s no need to install anything on Mac OS X version 10.2 and later. The system will always have the latest TWAIN.framework. For version 10.1.5 the source manager is supported only and you will need to install it seperately.


2. If no Source Manager is currently installed, install the Source Manager sent out with your application.

3. If a Source Manager already exists, check the version of the installed Source Manager. If the version provided with your application is more recent, rename the existing one as follows and install the Source Manager you shipped. To rename the existing Source Manager:On Windows systems:Rename the four files to be TWAIN.BAK, TWAIN_32.BAK, TWUNK_16.BAK, and TWUNK_32.BAK.On Macintosh systems: Move the Source Manager to the Extensions (Disabled) folder.

How to Install the Source Manager on Microsoft Windows Systems

To allow the comparison of Source Manager versions, the Microsoft Windows Source Manager DLL has version information built into it which conforms to the Microsoft File Version Stamping specification. Application developers are strongly encouraged to take advantage of this in their installation programs. Microsoft provides the File Version Stamping Library, VER.DLL, which should be used to install the Source Manager.

VER.DLL, VER.LIB and VER.H are included in this Toolkit; VER.DLL may be freely copied and distributed with your installation program. Of course, your installation program will have to link to this DLL to use it. Documentation on the File Version Stamping Library API can be found on the Microsoft Windows SDK.

The following code fragment demonstrates how the VerInstallFile( ) function provided in VER.DLL can be used to install the Source Manager into the user’s Windows directory.

The following example assumes that your installation floppy disk is in the A: drive and the Source Manager is in the root of the installation disk.

#include "windows.h"#include "ver.h"

#include "stdio.h"

// Max file name length is based on 8 dot 3 file name convention.

#define MAXFNAMELEN 12

// Max path name length is based on GetWindowsDirectory()

// documentation.

#define MAXPATHLEN 144

VOID InstallWinSM ( VOID )

{

DWORD dwInstallResult;

WORD wTmpFileLen = MAXPATHLEN;

WORD wLen;

char szSrcDir[MAXPATHLEN];

char szDstDir[MAXPATHLEN];


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char szCurDir[MAXPATHLEN];

char szTmpFile[MAXPATHLEN];

wLen = GetWindowsDirectory( szDstDir, MAXPATHLEN );

if (!wLen || wLen>MAXPATHLEN)

{

return; // failure getting Windows dir

}

strcpy( szCurDir, szDstDir );

strcpy( szSrcDir, "a:\\" );

dwInstallResult = VerInstallFile( VIFF_DONTDELETEOLD,

"TWAIN_32.DLL",

"TWAIN_32.DLL",

szSrcDir,

szDstDir,

szCurDir,

szTmpFile,

&wTmpFileLen );

// If VerInstallFile() left a temporary copy of the new

// file in DstDir be sure to delete it. This happens

// when a more recent version is already installed.

if ( dwInstallResult & VIF_TEMPFILE &&

((wTmpFileLen - MAXPATHLEN) > MAXFNAMELEN) )

{

// when dst path is root it already ends in ‘\’

if (szDstDir[wLen-1] != '\\')

{

strcat( szDstDir, "\\" );

}

strcat( szDstDir, szTmpFile );

remove( szDstDir );

}

}

You should enhance the above code so that it handles the other three files (TWAIN.DLL, TWUNK_16.EXE, and TWUNK_32.EXE), as well as fixing it to handle low memory and other error conditions, as indicated by the dwInstallResult return code. Also note that the above code does not leave a backup copy of the user’s prior Source Manager on their disk, but you should do this. Copy the older versions to TWAIN.BAK, TWAIN_32.BAK, TWUNK_16.BAK, and TWUNK_32.BAK.


How to Install the Source Manager on Macintosh Systems

For Mac OS X version 10.2 and later, the Source Manager is installed automatically with the OS and developers should not install or modify TWAIN.framework. For Mac OS X version 10.1.5, developers will need to follow these instructions to install the Source Manager.

The file TWAIN Source Manager should be installed in the Extensions folder of the active System Folder, if the version being installed is newer than the existing version, or there is no previous version of this file.

The folder TWAIN Data Sourcesshould be created in the Extensions folder if it does not exist.

If you are a scanner vendor, install your scanner data sources into the Extensions:TWAIN Data Sources: folder you created.

The file Source Manager should be installed in the Preferences:TWAIN: folder if it does not exist, or if its version number is higher than the existing file.

The last step is very important. The file you are installing is the 68k shim file that routes calls made by older applications to the new DSM. Without this file, older applications will not be able to use the TWAIN DSM properly.

Changes Needed to Prepare for a TWAIN SessionThere are three areas of the application that must be changed before a TWAIN session can even begin. The application developer must:

• Alter the application’s user interface to add Select Source and Acquire menu choices.

• Include the file called TWAIN.H in your application.

• Alter the application’s event loop.

Alter the Application’s User Interface to Add Select Source and Acquire Options

As mentioned in the Chapter 2, "Technical Overview,” the application should include two menu items in its File menu: Select Source... and Acquire.... It is strongly recommended that you use these phrases since this consistency will benefit all users.

Figure 3-1 User Interface for Selecting a Source and Acquiring Options


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Note the following:

Detailed information on the operations used by the application to successfully acquire data is provided later in this chapter in “Controlling a TWAIN Session from Your Application” on page 3-15.

Include the TWAIN.H File in Your Application

The TWAIN.H file that is shipped with this TWAIN Developer’s Toolkit contains all of the critical definitions needed for writing a TWAIN-compliant application or Source. Be sure to include it in your application’s code and print out a copy to refer to while reading this chapter.

The TWAIN.H file contains:

Category Prefix for each item

Data Groups DG_

Data Argument Types DAT_

Messages MSG_

Capabilities CAP_, ICAP_, or ACAP_

Return Codes TWRC_

Condition Codes TWCC_

Type Definitions TW_

Structure Definitions TW_

Entry points These are DSM_Entry and DS_Entry

In addition, there are many constants defined in TWAIN.H which are not listed here.

Alter the Application’s Event Loop

Events include activities such as key clicks, mouse events, periodic events, accelerators, etc. Every TWAIN-compliant application on Windows needs an event loop. (On Windows, these actions are called messages but that can be confusing because TWAIN uses the term messages to describe the third parameter of an operation triplet. Therefore, we will refer to these key clicks, etc. as events in this section generically.) During a TWAIN session, the application opens one or more Sources. However, even if several Sources are open, the application should only have one Source enabled at any given time. That is the Source from which the user is attempting to acquire data.

When this is selected: The application does this:

Select Source... The application requests that the Source Manager’s Select Source Dialog Box appear (or it may display its own version). After the user selects the Source they want to use, control returns to the application.

Acquire... The application requests that the Source display its user interface. (Again, the application can create its own version of a user interface or display no user interface.)


Altering the event loop serves three purposes:

• Passing events from the application to the Source so it can respond to them

• Notifying the application when the Source is ready to transfer data or have its user interface disabled

• Notifying the application when a device event occurs.

Event Loop Modification - Events in State 4

Please note that with TWAIN 1.8 and the addition of the DG_CONTROL / DAT_NULL / MSG_DEVICEEVENT message, it is possible to receive events after the Source has been opened but before it has been enabled (State 4). However, these events will not be sent from the Source to the Application unless the Application has negotiated for specific events using CAP_DEVICEEVENTS. Events posted in this way must use the hWnd passed to them by the DG_CONTROL / DAT_PARENT / MSG_OPENDS message. Sources are required to have all device events turned off when they are opened to support backward compatibility with older TWAIN applications.

Event Loop Modification - Passing events (The first purpose)

While a Source is enabled, all events are sent to the application’s event loop. Some of the events may belong to the application but others belong to the enabled Source. To ensure that the Source receives and processes its events, the following changes are required:

The application must send all events that it receives in its event loop to the Source as long as the Source is enabled. The application uses:

DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT

The TW_EVENT data structure used looks like this:

typedef struct { TW_MEMREF pEvent; /* Windows pMSG */ TW_UINT16 TWMessage; /* TW message from Source to */ /* the application */} TW_EVENT, FAR *pTW_EVENT;

The pEvent field points to the message structure.

The Source receives the event from the Source Manager and determines if the event belongs to it.

• If it does, the Source processes the event. It then sets the Return Code to TWRC_DSEVENT to indicate it was a Source event. In addition, it should set the TWMessage field of the TW_EVENT structure to MSG_NULL.

• If it does not, the Source sets the Return Code to TWRC_NOTDSEVENT meaning it is not a Source event. In addition, it should set the TWMessage field of the TW_EVENT structure to MSG_NULL. The application receives this information from DSM_Entry and should process the event in its event loop as normal.


Chapter 3

Event Loop Modification - Notifications from Source to application (The second and third purpose)

When the Source has data ready for a data transfer or it wishes to request that its user interface be disabled, it needs to communicate this information to the application asynchronously.

These notifications appear in the application’s event loop. They are contained in the TW_EVENT.TWMessage field. The four notices of interest are:

• MSG_XFERREADY to indicate data is ready for transfer

• MSG_CLOSEDSREQ to request that the Source’s user interface be disabled

• MSG_CLOSEDSOK to request that the Source’s user interface be disabled (special case for use with DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDSUIONLY).

• MSG_DEVICEEVENT to report that a device event has occurred.

Therefore, the application’s event loop must always check the TW_EVENT.TWMessage field following a DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT call to determine if it is the simple MSG_NULL or critical MSG_XFERREADY or MSG_CLOSEDSREQ. Information about how the application should respond to these two special notices is detailed later in this chapter in the “Controlling a TWAIN Session from Your Application” on page 3-15.”

How to Modify the Event Loop for Microsoft Windows

This section illustrates typical modifications needed in an Microsoft Windows application to support TWAIN-connected Sources.

TW_EVENT twEvent;TW_INT16 rc;while (GetMessage ( (LPMSG) &msg, NULL, 0, 0) ) { rc = TWRC_NOTDSEVENT; if Source is enabled { twEvent.pEvent = (TW_MEMREF)&msg; twEvent.TWMessage = MSG_NULL; rc = (*pDSM_Entry) (pAppId, pSourceId, DG_CONTROL, DAT_EVENT, MSG_PROCESSEVENT, (TW_MEMREF)&twEvent); // check for message from Source switch (twEvent.TWMessage) { case MSG_XFERREADY: SetupAndTransferImage(NULL); break; case MSG_CLOSEDSREQ: DisableAndCloseSource(NULL); break; case MSG_CLOSEDSOK: DisableAndCloseSource(NULL);


GetCustomDsData(); break; case MSG_NULL: // no message returned from the source break; } } // Source didn’t process it, so we will if (rc == TWRC_NOTDSEVENT) { TranslateMessage( (LPMSG) &msg); DispatchMessage( (LPMSG) &msg); }}

Note: Source writers are advised to keep stack space usage to a minimum. Application writers should also be aware that, in the Windows environment, sources run in their calling application’s data space. They depend upon the application to reserve enough stack space for the source to be able to perform its various functions. For this reason, applications should define enough stack space in their linker DEF files for the sources that they might use.

Two new TWAIN triplets exist to support the new event handling mechanism:

• DG_CONTROL / DAT_CALLBACK / MSG_REGISTER_CALLBACK

• DG_CONTROL / DAT_CALLBACK / MSG_INVOKE_CALLBACK

A Cocoa or Carbon Event Manager application will register the callback after opening the DS using the DG_CONTROL/ DAT_CALLBACK/ MSG_REGISTER_CALLBACK triplet, and a Carbon DS will invoke the callback using the DG_CONTROL/ DAT_CALLBACK/ MSG_INVOKE_CALLBACK triplet.

The callback function should look like this:

TW_UINT16 TWAIN_callback(pTW_IDENTITY pOrigin, pTW_IDENTITY pDest, TW_UINT32 DG, TW_UINT16 DAT, TW_UINT16 MSG,TW_MEMREF pData)

{ // process message the same as if it was received through // the event loop return TWRC_SUCCESS; // or failure etc}

An application would register the callback function with this code:

TW_CALLBACK callback = { 0 };callback.CallBackProc = TWAIN_callback;Result = DSM_Entry(&appIdentity, NULL, DG_CONTROL, DAT_CALLBACK, MSG_REGISTER_CALLBACK,


Chapter 3

(TW_MEMREF)&callback);The DS would invoke the callback thus:TW_CALLBACK callback = { 0 };callback.Message = MSG_XFERREADY;Result = DSM_Entry(&appIdentity, NULL, DG_CONTROL, DAT_CALLBACK, MSG_INVOKE_CALLBACK, (TW_MEMREF)&callback);DSM_Entry Call and Available Operation Triplets

As described in the Chapter 2, "Technical Overview,”all actions that the application invokes on the Source Manager or Source are routed through the Source Manager. The application passes the request for the action to the Source Manager via the DSM_Entry function call which contains an operation triplet describing the requested action. In code form, the DSM_Entry function looks like this:

On Windows:TW_UINT16 FAR PASCAL DSM_Entry ( pTW_IDENTITY pOrigin, // source of message pTW_IDENTITY pDest, // destination of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

On Macintosh:FAR PASCAL TW_UINT16 DSM_Entry

( pTW_IDENTITY pOrigin, // source of message pTW_IDENTITY pDest, // destination of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

The DG, DAT, and MSG parameters contain the operation triplet. The parameters must follow these rules:

pOriginReferences the application’s TW_IDENTITY structure. The contents of this structure must not be changed by the application from the time the connection is made with the Source Manager until it is closed.

pDestSet to NULL if the operation’s final destination is the Source Manager.Otherwise, set to point to a valid TW_IDENTITY structure for an open Source.

DG_xxxxData Group of the operation. Currently, only DG_CONTROL, DG_IMAGE, and DG_AUDIO are defined. Custom Data Groups can be defined.


DAT_xxxxDesignator that uniquely identifies the type of data object (structure or variable) referenced by pData.

MSG_xxxxMessage specifies the action to be taken.

pDataRefers to the TW_xxxx structure or variable that will be used during the operation. Its type is specified by the DAT_xxxx. This parameter should always be typecast to TW_MEMREF when it is being referenced.

Operation Triplets - Application to Source Manager

There are nine operation triplets that can be sent from the application to be consumed by the Source Manager. They all use the DG_CONTROL data group and they use three different data argument types: DAT_IDENTITY, DAT_PARENT, and DAT_STATUS. The following table lists the data group, data argument type, and messages that make up each operation. The list is in alphabetical order not the order in which they are typically called by an application. Details about each operation are available in reference format in Chapter 7, "Operation Triplets.”

Control Operations from Application to Source Manager

DG_CONTROL / DAT_IDENTITY

MSG_CLOSEDS : Prepare specified Source for unloading

MSG_GETDEFAULT : Get identity information of the default Source

MSG_GETFIRST : Get identity information of the first available Source

MSG_GETNEXT : Get identity of the next available Source

MSG_OPENDS : Load and initialize the specified Source

MSG_USERSELECT : Present “Select Source” dialog

DG_CONTROL / DAT_PARENT

MSG_CLOSEDSM : Prepare Source Manager for unloading

MSG_OPENDSM : Initialize the Source Manager

DG_CONTROL / DAT_STATUS

MSG_GET : Return Source Manager’s current Condition Code

Operation Triplets - Application to Source

The next group of operations are sent to a specific Source by the application. These operations are still passed via the Source Manager using the DSM_Entry call. The first set of triplets use the DG_CONTROL identification for their data group. These are operations that could be performed on any kind of TWAIN device. The second set of triplets use the DG_IMAGE identification for their data group which indicates these operations are specific to image data. Details about each operation are available in reference format in Chapter 7, "Operation Triplets”.


Chapter 3

Control Operations from Application to Source

DG_CONTROL / DAT_CAPABILITY

MSG_GET Return a Capability’s valid value(s) including current and default values

MSG_GETCURRENT Get a Capability’s current value

MSG_GETDEFAULT Get a Capability’s preferred default value (Source specific)

MSG_RESET Change a Capability’s current value to its TWAIN-defined default (See Chapter 10, "Capabilities.”)

MSG_SET Change a Capability’s current and/or available value(s)

DG_CONTROL / DAT_DEVICEEVENT

MSG_GET: Get an event from the Source (issue this call only in response to a DG_CONTROL / DAT_NULL / MSG_DEVICEEVENT from the Source)

DG_CONTROL / DAT_EVENT

MSG_PROCESSEVENT Pass an event to the Source from the application

DG_CONTROL / DAT_FILESYSTEM

MSG_AUTOMATICCAPTUREDIRECTORY Select directory to receive automatically captured images

MSG_CHANGEDIRECTORY Change the current domain, host, directory, or device.

MSG_COPY Copy files

MSG_CREATEDIRECTORY Create a directory

MSG_DELETE Delete a file or directory

MSG_FORMATMEDIA Format a storage device

MSG_GETCLOSE Close a context created by a call to MSG_GETFILEFIRST

MSG_GETFIRSTFILE Get the first file in a directory

MSG_GETINFO Get information about the current file context

MSG_RENAME Rename a file

DG_CONTROL / DAT_PASSTHRU / MSG_PASSTHRU

MSG_PASSTHRU Special command for the use by Source vendors when writing diagnostic Applications

DG_CONTROL / DAT_PENDINGXFERS

MSG_ENDXFER Application acknowledges or requests the end of data transfer

MSG_GET Return the number of transfers the Source is ready to supply

MSG_RESET Set the number of pending transfers to zero

MSG_STOPFEEDER Stop ADF without ending session


DG_CONTROL / DAT_SETUPFILEXFER

MSG_GET Return info about the file that the Source will write the acquired data into

MSG_GETDEFAULT Return the default file transfer information

MSG_RESET Reset current file information to default values

MSG_SET Set file transfer information for next file transfer

DG_CONTROL / DAT_SETUPMEMXFER

MSG_GET Return Source’s preferred, minimum, and maximum transfer buffer sizes

DG_CONTROL / DAT_STATUS

MSG_GET Return the current Condition Code from specified Source

DG_CONTROL / DAT_USERINTERFACE

MSG_DISABLEDS Cause Source’s user interface to be taken down

MSG_ENABLEDS Cause Source to prepare to display its user interface

DG_CONTROL / DAT_XFERGROUP

MSG_GET Return the Data Group (currently DG_IMAGE or a custom data group) for the upcoming transfer

There are five more DG_CONTROL operations for communications between the Source Manager and the Source. They are discussed in Chapter 5, "Source Implementation.”.

Image Operations from Application to Source

DG_IMAGE / DAT_CIECOLOR

MSG_GET Return the CIE XYZ information for the current transfer

DG_IMAGE / DAT_GRAYRESPONSE

MSG_RESET Reinstate identity response curve for grayscale data

MSG_SET Source uses specified response curve on grayscale data

DG_IMAGE / DAT_IMAGEFILEXFER

MSG_GET Initiate image acquisition using the Disk File transfer mode

DG_IMAGE / DAT_IMAGEINFO

MSG_GET Return information that describes the image for the next transfer

DG_IMAGE / DAT_IMAGELAYOUT

MSG_GET Describe physical layout / position of “original” image

MSG_GETDEFAULT Default information on the layout of the image

MSG_RESET Set layout information for the next transfer to defaults

MSG_SET Set layout for the next image transfer


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DG_IMAGE / DAT_IMAGEMEMXFER

MSG_GET Initiate image acquisition using the Buffered Memory transfer mode

DG_IMAGE / DAT_IMAGEMEMFILEXFER

MSG_GET Initiate image acquisition using the Buffered Memory transfer mode, but transferring the same data one would save to a file

DG_IMAGE / DAT_IMAGENATIVEXFER

MSG_GET Initiate image acquisition using the Native transfer mode

DG_IMAGE / DAT_JPEGCOMPRESSION

MSG_GET Return JPEG compression parameters for current transfer

MSG_GETDEFAULT Return default JPEG compression parameters

MSG_RESET Use Source’s default JPEG parameters on JPEG transfers

MSG_SET Use specified JPEG parameters on JPEG transfers

DG_IMAGE / DAT_PALETTE8

MSG_GET Return palette information for current transfer

MSG_GETDEFAULT Return Source’s default palette information for current pixel type

MSG_RESET Use Source’s default palette for transfer of this pixel type

MSG_SET Use specified palette for transfers of this pixel type

DG_IMAGE / DAT_RGBRESPONSE

MSG_RESET Use Source’s default (identity) RGB response curve

MSG_SET Use specified response curve for RGB transfers

DG_AUDIO / DAT_AUDIOFILEXFER

MSG_GET Transfers audio data in file mode

DG_AUDIO / DAT_AUDIOINFO

MSG_GET Gets information about the current transfer

DG_AUDIO / DAT_AUDIONATIVEXFER

MSG_GET Transfers audio data in native mode

DSM_Entry Parameters

The parameters for the DG_xxxx, DAT_xxxx, and MSG_xxxx fields are determined by the operation triplet. The other parameters are filled as follows:

• pOrigin

Refers to a copy of the application’s TW_IDENTITY structure.

• pDest


If the operation’s destination is the Source Manager: Always holds a value of NULL. This indicates to the Source Manager that the operation is to be consumed by it not passed on to a Source.If the operation’s destination is a Source: This parameter references a copy of the Source’s TW_IDENTITY structure that is maintained by the application. The application received this structure in response to the DG_CONTROL / DAT_IDENTITY / MSG_OPENDS operation sent from the application to the Source Manager. This is discussed more in the next section (“Controlling a TWAIN Session from Your Application” - State 3 to 4).

• pData

Always references a structure or variable corresponding to the TWAIN type specified by the DAT_xxxx parameter. Typically, but not always, the data argument type name corresponds to a TW_xxxx data structure name. For example, the DAT_IDENTITY argument type uses the corresponding TW_IDENTITY data structure. All data structures can be seen in the file called TWAIN.H. The application is responsible for allocating and deallocating the structure or element and assuring that pData correctly references it.Note that there are two cases when the Source, rather than the application, allocates a structure that is used during an operation.

• One occurs during DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, and MSG_RESET operations. The application still allocates *pData but the Source allocates a structure referenced by *pData called a “container structure”.

• The other occurs during the DG_IMAGE / DAT_JPEGCOMPRESSION operations. The topic of data compression is covered in Chapter 4, "Advanced Application Implementation.”

In all cases, the application still deallocates all structures.

Controlling a TWAIN Session from Your ApplicationIn addition to the preparations discussed at the beginning of this chapter, the application must be modified to actually initiate and control a TWAIN session.

The session consists of the seven states of the TWAIN protocol as introduced in the Technical Overview. However, the application is not forced to move the session from State 1 to State 7 without stopping. For example, some applications may choose to pause in State 3 and move among the higher states (4 - 7) to repeatedly open and close Sources when acquisitions are requested by the user. Another example of session flexibility occurs when an application transfers multiple images during a session. The application will repeatedly move the session from State 6 to State 7 then back to State 6 and forward to State 7 again to transfer the next image.

For the sake of simplicity, this chapter illustrates moving the session from State 1 to State 7 and then backing it out all the way from State 7 to State 1. The diagram on the next page shows the operation triplets that are used to transition the session from one state to the next. Detailed information about each state and its associated transitions follow. The topics include:

• State 1 to 2 - Load the Source Manager and Get the DSM_Entry

• State 2 to 3 - Open the Source Manager


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• State 3 - Select the Source

• State 3 to 4 - Open the Source

• State 4 - Negotiate Capabilities with the Source

• State 4 to 5 - Request the Acquisition of Data from the Source

• State 5 to 6 - Recognize that the Data Transfer is Ready

• State 6 to 7 - Start and Perform the Transfer

• State 7 to 6 to 5 - Conclude the Transfer

• State 5 to 1 - Disconnect the TWAIN Session

Note: Sources and Applications that support the DAT_FILESYSTEM operation may negotiate and select different device contexts immediately after the opening of a Source. For example, an Application may choose to browse through the stored images on a digital camera, rather than treat it as a real-time capture device.


Figure 3-2 TWAIN States

State 1 to 2 - Load the Source Manager and Get the DSM_Entry

The application must load the Source Manager before it is able to call its DSM_Entry point.

Operations Used:

No TWAIN operations are used for this transition. Instead,


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On Windows:Load TWAIN_32.DLL using the LoadLibrary( ) routine. Get the DSM_Entry by using the GetProcAddress( ) call.

On Macintosh:Link against TWAIN.framework.

On Windows:

The application can load the Source Manager by doing the following:

DSMENTRYPROC pDSM_Entry;HANDLE hDSMLib;char szSMDir;OFSTRUCT of;// check for the existence of the TWAIN_32.DLL file in the Windows // directory GetWindowsDirectory (szSMDir, sizeof(szSMDir)); /*** Could have been networked drive with trailing ‘\’ ***/ if (szSMDir [(lstrlen (szSMDir) - 1)] != ‘\\’) { lstrcat( szSMDir, "\\" ); }if ((OpenFile(szSMDir, &of, OF_EXIST) != -1) { // load the DLL if (hDSMDLL = LoadLibrary(“TWAIN_32.DLL”)) != NULL) { // check if library was loaded if (hDSMDLL >= (HANDLE)VALID_HANDLE) { if (lpDSM_Entry = (DSMENTRYPROC)GetProcAddress(hDSMDLL, MAKEINTRESOURCE (1))) != NULL) { if (lpDSM_Entry ) FreeLibrary(hDSMDLL); } } }}

Note, the code appends TWAIN_32.DLL to the end of the Windows directory and verifies that the file exists before calling LoadLibrary( ). Applications are strongly urged to perform a dynamic run-time link to DSM_Entry( ) by calling LoadLibrary( ) rather than statically linking to TWAIN_32.LIB via the linker. If the TWAIN_32.DLL is not installed on the machine, Microsoft Windows will fail to load an application that statically links to TWAIN_32.LIB. If the Application has a dynamic link, however, it will be able to give users a meaningful error message, and perhaps continue with image acquisition facilities disabled.

After getting the DSM_Entry, the application must check pDSM_Entry. If it is NULL, it means that the Source Manager has not been installed on the user’s machine and the application cannot provide any TWAIN services to the user. If NULL, the application must not attempt to call *pDSM_Entry as this would result in an Unrecoverable Application Error (UAE).


On Macintosh:

The Source Manager is a mach-o framework (TWAIN.framework).

When building your application, you should link against TWAIN.framework. There should be no need to check for an existing Source Manager - beginning with Mac OS X 10.2, the TWAIN.framework is part of Mac OS X.

State 2 to 3 - Open the Source Manager

The Source Manager has been loaded. The application must now open the Source Manager.

One Operation is Used:


pOriginThe application must allocate a structure of type TW_IDENTITY and fill in all fields except

for the Id field. Once the structure is prepared, this pOrigin parameter should point at that structure.

During the MSG_OPENDSM operation, the Source Manager will fill in the Id field with a unique identifier of the application. The value of this identifier is only valid while the application is connected to the Source Manager.

The application must save the entire structure. From now on, the structure will be referred to by the pOrigin parameter to identify the application in every call the application makes to DSM_Entry( ).

The TW_IDENTITY structure is defined in the TWAIN.H file but for quick reference, it looks like this:

/* DAT_IDENTITY Identifies the program/library/code *//* resource. */typedef struct { TW_UINT32 Id; /* Unique number for identification*/ TW_VERSION Version; TW_UINT16 ProtocolMajor; TW_UINT16 ProtocolMinor; TW_UINT32 SupportedGroups;/*Bit field OR combination */ /*of DG_constants found in */ /*the TWAIN.H file */ TW_STR32 Manufacturer; TW_STR32 ProductFamily; TW_STR32 ProductName;} TW_IDENTITY, FAR *pTW_IDENTITY;

pDestSet to NULL indicating the operation is intended for the Source Manager.

pData

Typically, you would expect to see this point to a structure of type TW_PARENT but this is not the case. This is an exception to the usual situation where the DAT field of the triplet identifies the data structure for pData.


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• On Windows: pData points to the window handle (hWnd) that will act as the Source’s “parent”. The variable is of type TW_INT32. For 16 bit Microsoft Windows, the handle is stored in the low word of the 32 bit integer and the upper word is set to zero. If running under the WIN32 environment, this is a 32 bit window handle. The Source Manager will maintain a copy of this window handle for posting messages back to the application.

• On Macintosh: pData should be a 32-bit NULL value.

How to Initialize the TW_IDENTITY Structure

Here is a Windows example of code used to initialize the application’s TW_IDENTITY structure.

TW_IDENTITY AppID; // App’s identity structure AppID.Id = 0; // Initialize to 0 (Source Manager // will assign real value) AppID.Version.MajorNum = 3; //Your app's version number AppID.Version.MinorNum = 5; AppID.Version.Language = TWLG_ENGLISH_USA; AppID.Version.Country = TWCY_USA; lstrcpy (AppID.Version.Info, "Your App's Version String"); AppID.ProtocolMajor = TWON_PROTOCOLMAJOR; AppID.ProtocolMinor = TWON_PROTOCOLMINOR; AppID.SupportedGroups = DF_APP2 | DG_IMAGE | DG_CONTROL; lstrcpy (AppID.Manufacturer, "App's Manufacturer"); lstrcpy (AppID.ProductFamily, "App's Product Family"); lstrcpy (AppID.ProductName, "Specific App Product Name");

On Windows: Using DSM_Entry to open the Source Manager

TW_UINT16 rc;rc = (*pDSM_Entry) (&AppID, NULL, DG_CONTROL, DAT_PARENT, MSG_OPENDSM, (TW_MEMREF) &hWnd);

where AppID is the TW_IDENTITY structure that the application set up to identify itself and hWnd is the application’s main window handle.

On Macintosh: Using DSM_Entry to open the Source Manager

rc = DSM_Entry(&AppID,

NULL,

DG_CONTROL,

DAT_PARENT,

MSG_OPENDSM,

NULL);

If your data source requires resources, it is responsible for loading and unloading them at run time. The Source Manager no longer manages resources automatically.


State 3 - Select the Source

The Source Manager has just been opened and is now available to assist your application in the selection of the desired Source.

DG_CONTROL / DAT_PARENT / MSG_OPENDSM. If it finds DF_DSM2 then the Application must issue the DG_CONTROL / DAT_ENTRYPOINT / MSG_GET call before it opens the Source. This takes the form:

DG_CONTROL / DAT_ENTRYPOINT / MSG_GET

pOrigin Points to the application’s TW_IDENTITY structure.

pDest Set to NULL.

pData Points to a structure of type TW_ENTRYPOINT

The Source Manager returns pointers to functions that the Application must use when managing memory that is either freed or allocated by the Source.



pOriginPoints to the application’s TW_IDENTITY structure. The desired data type should be specified by the application. This was done when you initialized the SupportedGroups field in your application’s TW_IDENTITY structure.This causes the Source Manager to make available for selection by the user only those Sources that can provide the requested data type(s). All other Sources are grayed out. (Note, if more than one data type were available, for example image and text, and the application wanted to accept both types of data, it would do a bit-wise OR of the types’ constants and place the results into the SupportedGroups field.)

pDestSet to NULL.

pDataPoints to a structure of type TW_IDENTITY. The application must allocate this structure prior to making the call to DSM_Entry. Once the structure is allocated, the application must:

• Set the Id field to zero.• Set the ProductName field to the null string (“\0”). (If the application wants a

specific Source to be highlighted in the Select Source dialog box, other than the system default, it can enter the ProductName of that Source into the ProductName field instead of null. The system default Source and other available Sources can be determined by using the DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULT, MSG_GETFIRST and MSG_GETNEXT operations.)


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Additional fields of the structure will be filled in by the Source Manager during this operation to identify the selected Source. Make sure the application keeps a copy of this updated structure after completing this call. You will use it to identify the Source from now on. The most common approach for selecting the Source is to use the Source Manager’s Select Source dialog box. This is typically displayed when the user clicks on your Select Source option. To do this:

1. The application sends a DG_CONTROL / DAT_IDENTITY / MSG_USERSELECT operation to the Source Manager to have it display its dialog box. The dialog displays a list of all Sources that are installed on the system that can provide data of the type specified by the application. It highlights the Source that is the system default unless the application requests otherwise.

2. The user selects a Source or presses the Cancel button. If no devices are available, the Select Source Dialog’s Select/OK button will be grayed out and the user will have no choice but to select Cancel.

3. The application must check the Return Code of DSM_Entry to determine the user’s action.

a: If TWRC_SUCCESS: Their selected Source is listed in the TW_IDENTITY structure pointed to by the pData parameter and is now the default Source.

b: If TWRC_CANCEL: The user either clicked Cancel intentionally or had no other choice because no devices were listed. Do not attempt to open a Source.

c: If TWRC_FAILURE: Use the DG_CONTROL / DAT_STATUS / MSG_GET operation (sent to the Source Manager) to determine the cause. The most likely cause is a lack of sufficient memory.

As an alternative to using the Source Manager’s Select Source dialog, the application can devise its own method for selecting a Source. For example, it could create and display its own user interface or simply select a Source without offering the user a choice. This alternative is discussed in Chapter 4, "Advanced Application Implementation.”

State 3 to 4 - Open the Source

The Source Manager is open and able to help your application open a Source.


DG_CONTROL / DAT_IDENTITY / MSG_OPENDS

pOriginPoints to the application’s TW_IDENTITY structure.

pDestSet to NULL.

pDataPoints to a structure of type TW_IDENTITY.Typically, this points to the application’s copy of the Source’s TW_IDENTITY structure filled in during the MSG_USERSELECT operation previously.


However, if the application wishes to have the Source Manager simply open the default Source, it can do this by setting the TW_IDENTITY.ProductName field to “\0” (null string) and the TW_IDENTITY.Id field to zero.During the MSG_OPENDS operation, the Source Manager assigns a unique identifier to the Source and records it in the TW_IDENTITY.Id field. Copy the resulting TW_IDENTITY structure. Once the Source is opened, the application will point to this resulting structure via the pDest parameter on every call that the application makes to DSM_Entry where the desired destination is this Source.

Note: The user is not required to take advantage of the Select Source option. They may click on the Acquire option without having selected a Source. In that case, your application should open the default Source. The default source is either the last one used by the user or the last one installed.

State 4 - Negotiate Capabilities with the Source

At this point, the application has a structure identifying the open Source. Operations can now be directed from the application to that Source. To receive a single image from the Source, only one capability, CAP_XFERCOUNT, must be negotiated now. All other capability negotiation is optional.

Note: M2 in its TW_IDENTITY.SupportedGroups, then the Application must use the DSM_MemAllocate, DSM_MemFree, DSM_MemLock and DSM_MemUnlock functions it got from DG_CONTROL / DAT_ENTRYPOINT / MSG_GET to manage any memory it uses with the Source.

Two Operations are Used:

DG_CONTROL / DAT_CAPABILITY / MSG_GET

DG_CONTROL / DAT_CAPABILITY / MSG_SET

The parameters for each of the operations, in addition to the triplet, are these:


pDestPoints to the desired Source’s TW_IDENTITY structure. The Source Manager will receive the DSM_Entry call, recognize that the destination is a Source rather than itself, and pass the operation along to the Source via the DS_Entry function.

pData

Points to a structure of type TW_CAPABILITY. The definition of TW_CAPABILITY is:

typedef struct { TW_UINT16 Cap; /* ID of capability to get or set */ TW_UINT16 ConType; /* TWON_ONEVALUE, TWON_RANGE, */ /* TWON_ENUMERATION or TWON_ARRAY */ TW_HANDLE hContainer; /* Handle to container of type */


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/* ConType */} TW_CAPABILITY, FAR *pTW_CAPABILITY;

The Source allocates the container structure pointed to by the hContainer field when called by the MSG_GET operation. The application allocates it when calling with the MSG_SET operation. Regardless of who allocated it, the application deallocates the structure either when the operation is complete or when the application no longer needs to maintain the information.

Each operation serves a special purpose:

MSG_GET

Since Sources are not required to support all capabilities, this operation can be used to determine if a particular TWAIN-defined capability is supported by a Source. The application needs to set the Cap field of the TW_CAPABILITY structure to the identifier representing the capability of interest. The constants identifying each capability are listed in the TWAIN.H file.

If the capability is supported and the operation is successful, it returns the Current, Default, and Available values. These values reflect previous MSG_SET operations on the capability which may have altered them from the TWAIN default values for the capability.

This operation may fail due to several causes. If the capability is not supported by the Source, the Return Code will be TWRC_FAILURE and the condition code will be one of the following:

TWCC_CAPUNSUPPORTED Capability not supported by Source

TWCC_CAPBADOPERATION Operation not supported by capability

TWCC_CAPSEQERROR Capability has dependency on other capability

Applications should be prepared to receive the condition code TWCC_BADCAP from Sources written prior to TWAIN 1.7, which maps to any of the three situations mentioned above.

MSG_SET

Changes the Current or Available Value(s) of the specified capability to those requested by the application. The application may choose to set just the capability’s Current Value or it may specify a list of values for the Source to use as the complete set of Available Values for that capability.

Note: Source is not required to limit values based on the application’s request although it is strongly recommended that they do so. If the Return Code indicates TWRC_FAILURE, check the Condition Code. A code of TWCC_BADVALUE can mean:

• The application sent an invalid value for this Source’s range.

• The Source does not allow the setting of this capability.

• The Source doesn’t allow the type of container used by the application to set this capability.

Capability negotiation gives the application developer power to guide the Source and control the images they receive from the Source. The negotiation typically occurs during State 4. The following material illustrates only one very basic capability and container structure. Refer to Chapter 4, "Advanced Application Implementation” for a more extensive discussion of capabilities including information on how to delay the negotiation of some capabilities beyond State 4.


Note: It is important here to once again remind application writers to always check the return code from any negotiated capabilities transactions.

Set the Capability to Specify the Number of Images the Application can Transfer

The capability that specifies how many images an application can receive during a TWAIN session is CAP_XFERCOUNT. All Sources must support this capability. Possible values for CAP_XFERCOUNT are:

The default value allows multiple images to be transferred. The following is a simple code example illustrating the setting of a capability and specifically showing how to limit the number of images to one. Notice there are differences between the code for Windows and Macintosh applications. Both versions are included here with ifdef statements for MSWIN versus MAC.

TW_CAPABILITY twCapability;TW_INT16 count;TW_STATUS twStatus;TW_UINT16 rc;#ifdef _MSWIN_pTW_ONEVALUE pval;#endif#ifdef _MAC_TW_HANDLE h;pTW_INT16 pInt16;#endif//-----Setup for MSG_SET for CAP_XFERCOUNTtwCapability.Cap = CAP_XFERCOUNT;twCapability.ConType = TWON_ONEVALUE;#ifdef _MSWIN_twCapability.hContainer = GlobalAlloc(GHND, sizeof(TW_ONEVALUE));pval = (pTW_ONEVALUE) GlobalLock(twCapability.hContainer);pval->ItemType = TWTY_INT16;pval->Item = 1; //This app will only accept 1 imageGlobalUnlock(twCapability.hContainer);#endif#ifdef _MAC_

twCapability.hContainer = (TW_HANDLE)h = NewHandle(sizeof(TW_ONEVALUE));((TW_ONEVALUE*)(*h))->ItemType = TWTY_INT16;

Value: Description:

1 Application wants to receive a single image.

greater than 1 Application wants to receive this specific number of images.

-1 Application can accept any arbitrary number of images during the session. This is the default for this capability.

0 This value has no legitimate meaning and the application should not set the capability to this value. If a Source receives this value during a MSG_SET operation, it should maintain the Current Value without change and return TWRC_FAILURE and TWCC_BADVALUE.


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count = 1; //This app will only accept 1 imagepInt16 = ((TW_ONEVALUE*)(*h))->Item;*pInt16 = count;#endif//-----Set the CAP_XFERCOUNTrc = (*pDSM_Entry) (&AppID, &SourceID, DG_CONTROL, DAT_CAPABILITY, MSG_SET, (TW_MEMREF)&twCapability);#ifdef _MSWIN_GlobalFree((HANDLE)twContainer.hContainer);#endif#ifdef _MAC_DisposHandle((HANDLE)twContainer.hContainer);#endif//-----Check Return Codes//SUCCESSif (rc == TWRC_SUCCESS) //the value was set//APPROXIMATION MADEelse if (rc == TWRC_CHECKSTATUS) { //The value could not be matched exactly //MSG_GET to get the new current value twCapability.Cap = CAP_XFERCOUNT; twCapability.ConType = TWON_DONTCARE16; //Source will specify twCapability.hContainer = NULL; //Source allocates and fills container rc = (*pDSM_Entry) (&AppID, &SourceID, DG_CONTROL, DAT_CAPABILITY, MSG_GET, (TW_MEMREF)&twCapability); //remember current value #ifdef _MSWIN_ pval = (pTW_ONEVALUE) GlobalLock(twCapability.hContainer); count = pval->Item; //free hContainer allocated by Source GlobalFree((HANDLE)twCapability.hContainer); #endif #ifdef _MAC_ pInt16 = ((TW_ONEVALUE*)(*h))->Item; count = *pInt16;


//free hContainer allocated by Source DisposeHandle((HANDLE)twCapability.hContainer); #endif }//MSG_SET FAILEDelse if (rc == TWRC_FAILURE) { //check Condition Code rc = (*pDSM_Entry) (&AppID, &SourceID, DG_CONTROL, DAT_STATUS, MSG_GET, (TW_MEMREF)&twStatus); switch (twStatus.ConditionCode) { TWCC_BADCAP: TWCC_CAPUNSUPPORTED: TWCC_CAPBADOPERATION: TWCC_CAPSEQERROR: //Source does not support setting this cap //All Sources must support CAP_XFERCOUNT break; TWCC_BADDEST: //The Source specified by pSourceID is not open break; TWCC_BADVALUE: //The value set was out of range for this Source //Use MSG_GET to determine what setting was made //See the TWRC_CHECKSTATUS case handled earlier break; TWCC_SEQERROR: //Operation invoked in invalid state break; } }

Other Capabilities

Image TypeAlthough not shown, the application should be aware of the Source’s ICAP_PIXELTYPE and ICAP_BITDEPTH. If your application cannot accept all of the Source’s Available Values, capability negotiation should be done. (Refer to Chapter 4, "Advanced Application Implementation.”)

Transfer ModeThe default transfer mode is Native. That means the Source will access the largest block of memory available and use it to transfer the entire image to the application at once. If the


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available memory is not large enough for the transfer, then the Source should fail the transfer. The application does not need to do anything to select this transfer mode. If the application wishes to specify a different transfer mode, Disk File or Buffered Memory, further capability negotiation is required. (Refer to Chapter 4, "Advanced Application Implementation.”)

State 4 to 5 - Request the Acquisition of Data from the Source

The Source device is open and capabilities have been negotiated. The application now enables the Source so it can show its user interface, if requested, and prepare to acquire data.


DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS


pDestPoints to the Source’s TW_IDENTITY structure.

pData

Points to a structure of type TW_USERINTERFACE. The definition of TW_USERINTERFACE is:

typedef struct { TW_BOOL ShowUI; TW_BOOL ModalUI; TW_HANDLE hParent; } TW_USERINTERFACE, FAR *pTW_USERINTERFACE;

Set the ShowUI field to TRUE if you want the Source to display its user interface. Otherwise, set to FALSE.The Application will set the ModalUI field to TRUE if it wants the Source to run modal, and FALSE if it wants the Source to run modeless. Please note that to successfully run modal, it may be necessary for the application to disable inputs to its windows while the Source’s GUI is running.The application sets the hParent field differently depending on the platform on which the application runs.

• On Windows - The application should place a handle to the Window that is acting as the Source’s parent.

• On Macintosh - The application sets this field to NULL.

In response to the user choosing the application’s Acquire menu option, the application sends this operation to the Source to enable it. The application typically requests that the Source display the Source’s user interface to assist the user in acquiring data. If the Source is told to display its user interface, it will display it when it receives the operation triplet. Modal and Modeless interfaces are discussed in Chapter 4, "Advanced Application Implementation” and Chapter 5, "Source Implementation.” Sources must check the ShowUI field and return an error if they cannot support the specified mode. In other words it is unacceptable for a source to ignore a ShowUI = FALSE request and still activate its user interface. The application may


develop its own user interface instead of using the Source’s. This is discussed in Advanced Application Implementation.”

Note: Once the Source is enabled via the DG_CONTROL / DAT_USERINTERFACE/ MSG_ENABLEDS operation, all events that enter the application’s main event loop must be immediately forwarded to the Source. The explanation for this was given earlier in this chapter when you were instructed to modify the event loop in preparation for a TWAIN session.

State 5 to 6 - Recognize that the Data Transfer is Ready

The Source is now working with the user to arrange the transfer of the desired data. Unlike all the earlier transitions, the Source, not the application, controls the transition from State 5 to State 6.

No Operations (from the application) are Used:

This transition is not triggered by the application sending an operation. The Source causes the transition.

Remember while the Source is enabled, the application is forwarding all events in its event loop to the Source by using the DG_CONTROL /DAT_EVENT / MSG_PROCESSEVENT operation. The TW_EVENT data structure associated with this operation looks like this:

typedef struct { TW_MEMREF pEvent; /*Windows pMSG or MAC pEvent */ TW_UINT16 TWMessage;/*TW message from the Source to the application*/} TW_EVENT, FAR *pTW_EVENT;

The Source can set the TWMessage field to signal when the Source is ready to transfer data. Following each DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT operation, the application must check the TWMessage field. If it contains MSG_XFERREADY, the session is in State 6 and the Source will wait for the application to request the actual transfer of data.

State 6 to 7 - Start and Perform the Transfer

The Source indicated it is ready to transfer data. It is waiting for the application to inquire about the image details, initiate the actual transfer, and, hence, transition the session from State 6 to 7. If the initiation (DG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET) fails, the session does not transition to State 7 but remains in State 6.

Two Operations are Used:

DG_IMAGE / DAT_IMAGEINFO / MSG_GET




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pData

Points to a structure of type TW_IMAGEINFO. The definition of TW_IMAGEINFO is:typedef struct { TW_FIX32 XResolution; TW_FIX32 YResolution; TW_INT32 ImageWidth; TW_INT32 ImageLength; TW_INT16 SamplesPerPixel; TW_INT16 BitsPerSample[8]; TW_INT16 BitsPerPixel; TW_BOOL Planar; TW_INT16 PixelType; TW_UINT32 Compression; } TW_IMAGEINFO, FAR *pTW_IMAGEINFO;

The Source will fill in information about the image that is to be transferred. The application uses this operation to get the information regardless of which transfer mode (Native, Disk File, or Buffered Memory) will be used to transfer the data.

DG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET



pDataPoints to a TW_UINT32 variable. This is an exception from the typical pattern.

• On Windows: This is a pointer to a handle variable. For 16 bit Microsoft Windows, the handle is stored in the low word of the 32-bit integer and the upper word is set to zero. If running under the WIN32 environment, this is a 32 bit window handle. The Source will set pHandle to point to a device-independent bitmap (DIB) that it allocates.

• On Macintosh: This is a pointer to a PicHandle. The Source will set pHandle to point to a PicHandle that the Source allocates.

In either case, the application is responsible for deallocating the memory block holding the Native-format image.

The application may want to inquire about the image data that it will be receiving. The DG_IMAGE / DAT_IMAGEINFO / MSG_GET operation allows this. Other operations, such as DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET, provide additional information. This information can be used to determine if the application actually wants to initiate the transfer.

To actually transfer the data in the Native mode, the application invokes the DG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET operation. The Native mode is the default transfer mode and will be used unless a different mode was negotiated via capabilities in State 4. For the Native mode transfer, the application only invokes this operation once per image. The Source returns the TWRC_XFERDONE value when the transfer is complete. This type of transfer cannot be aborted by the application once initiated. (Whether it can be aborted from the Source’s User Interface depends on the Source.) Use of the other transfer modes, Disk File and Buffered Memory, are discussed in Chapter 4, "Advanced Application Implementation.”


The following code illustrates how to get information about the image that will be transferred and how to actually perform the transfer. This code segment is continued in the next section (State 7 to 6 to 5).

// After receiving MSG_XFERREADY

TW_UINT16 TransferNativeImage()

{

TW_IMAGEINFO twImageInfo;

TW_UINT16 rc;

TW_UINT32 hBitmap;

TW_BOOL PendingXfers = TRUE;while (PendingXfers){ rc = (*pDSM_Entry)(&AppId, &SourceId, DG_IMAGE, DAT_IMAGEINFO, MSG_GET, (TW_MEMREF)&twImageInfo); if (rc == TWRC_SUCCESS) Examine the image information // Transfer the image natively hBitmap = NULL; rc = (*pDSM_Entry)(&AppId, SourceId, DG_IMAGE, DAT_IMAGENATIVEXFER, MSG_GET, (TW_MEMREF)&HbITMAP); // Check the return code switch(rc) { case TWRC_XFERDONE: // Notes: hBitmap points to a valid image Native image (DIB or // PICT) // The application is now responsible for deallocating the memory. // The source is currently in state 7. // The application must now acknowledge the end of the transfer, // determine if other transfers are pending and shut down the data // source. PendingXfers = DoEndXfer(); //Function found in code //example in next section

break; case TWRC_CANCEL: // The user canceled the transfer. // hBitmap is an invalid handle but memory was allocated. // Application is responsible for deallocating the memory.


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// The source is still in state 7. // The application must check for pending transfers and shut down // the data source. PendingXfers = DoEndXfer(); //Function found in code //example in next section break; case TWRC_FAILURE: // The transfer failed for some reason. // hBitmap is invalid and no memory was allocated. // Condition code will contain more information as to the cause of // the failure. // The state transition failed, the source is in state 6. // The image data is still pending. // The application should abort the transfer. DoAbortXfer(MSG_RESET); //Function in next section PendingXfers = FALSE; break; } }}//Check the return codeswitch (rc) { case TWRC_XFERDONE: //hBitMap points to a valid Native Image (DIB or PICT) //The application is responsible for deallocating the memory //The source is in State 7 //Acknowledge the end of the transfer goto LABEL_DO_ENDXFER //found in next section break; case TWRC_CANCEL: //The user canceled the transfer //hBitMap is invalid //The source is in State 7 //Acknowledge the end of the transfer goto LABEL_DO_ENDXFER //found in next section break; case TWRC_FAILURE: //The transfer failed //hBitMap is invalid and no memory was allocated //Check Condition Code for more information //The state transition failed, the source is in State 6 //The image data is still pending //To abort the transfer goto LABEL_DO_ENDXFER //found in code example for //the next section


break; }

State 7 to 6 to 5 - Conclude the Transfer

While the transfer occurs, the session is in State 7. When the Source indicates via the Return Code that the transfer is done (TWRC_XFERDONE) or canceled (TWRC_CANCEL), the application needs to transition the session backwards.


DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER



pDataPoints to a structure of type TW_PENDINGXFERS.

The DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation is sent by the application to the Source at the end of every transfer, successful or canceled, to indicate the application has received all the data it expected.

After this operation returns, the application should examine the pData->Count field to determine if there are more images waiting to be transferred. The value of pData->Count indicates the following:

Value Description

pData->Count = 0 If zero, the Source will “automatically” transition back to State 5 without the application needing to take any additional action. Application writers please make special note of this instance of an implied source transition.The application should return to its main event loop and await notification from the Source (either MSG_XFERREADY or MSG_CLOSEDSREQ).


Chapter 3

If more images were pending and your application does not wish to transfer all of them, you can discard one or all pending images by doing the following:

• To discard just the next pending image, use the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation. Then, check the Count field again to determine if there are additional images pending.

• To discard all pending images, use the DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET operation. Following successful execution of this operation, the session will be in State 5.

The following code is a continuation of the code example started in the State 6 to 7 section. It illustrates how to conclude the transfer.

void DoEndXfer(){ TW_PENDINGXFERS twPendingXfers; // If the return code from DG_IMAGE/DAT_IMAGENATIVEXFER/MSG_GET was // TWRC_CANCEL or TWRC_DONE // Acknowledge the end of the transfer rc = (*pDSM_Entry)(&AppId, SourceId, DG_CONTROL, DAT_PENDINGXFERS, MSG_ENDXFER, (TW_MEMREF)&twPendingXfers); if (rc == TWRC_SUCCESS) { // Check for additional pending xfers if (twPendingXfers.Count == 0) { // Source is now in state 5. NOTE THE IMPLIED STATE // TRANSITION! Disable and close the source and // return to TransferNativeImage with a FALSE notifying // it to not attempt further image transfers.

pData->Count = -1 orpData->Count > 0

The Source has more transfers available and is waiting in State 6.If the value is -1, that means the Source has another image available but it is unsure of how many more will be available. This might occur if the Source was controlling a device equipped with a document feeder and some unknown number of documents were stacked in that feeder. If the number of images is known, the Count will be a value greater than 0.Either way, the Source will remain in State 6 ready for the application to initiate another transfer. The Source will NOT send another MSG_XFERREADY to trigger this. The application should proceed as if it just received a MSG_XFERREADY.

Value Description


DisableAndCloseDS(); return(FALSE); } else { // Source is in state 6 ready to transfer another image if want to transfer this image { // returns to the caller, TransferNativeImage // and allows the next image to transfer return TRUE; } else if want to abort and skip over this transfer { // The current image will be skipped, and the // next, if exists will be acquired by returning // to TransferNativeImage if (DoAbortXfer(MSG_ENDXFER) > 0) return(TRUE); else return(FALSE); } } } }}TW_UINT16 DoAbortXfer(TW_UINT16 AbortType){ rc = (*pDSM_Entry)(&AppId, SourceId, DG_CONTROL, DAT_PENDINGXFERS, MSG_ENDXFER, (TW_MEMREF)&twPendingXfers); if (rc == TWRC_SUCCESS) { // If the next image is to be skipped, but subsequent images // are still to be acquired, the PendingXfers will receive // the MSG_ENDXFER, otherwise, PendingXfers will receive // MSG_RESET. rc = (*pDSM_Entry)(&AppId, SourceId, DG_CONTROL, DAT_PENDINGXFERS, AbortType, (TW_MEMREF)&twPendingXfers);


Chapter 3

}}//To abort all pending transfers:LABEL_ABORT_ALL: { rc = (*pDSM_Entry) (&AppID, &SourceID, DG_CONTROL, DAT_PENDINGXFERS, MSG_RESET, (TW_MEMREF)&twPendingXfers); if (rc == TWRC_SUCCESS) //Source is now in state 5 }}

State 5 to 1 - Disconnect the TWAIN Session

Once the application has acquired all desired data from the Source, the application can disconnect the TWAIN session. To do this, the application transitions the session backwards.

In the last section, the Source transitioned to State 5 when there were no more images to transfer (TW_PENDINGXFERS.Count = 0) or the application called the DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET operation to purge all remaining transfers. To back out the remainder of the session:

Three Operations (plus some platform-dependent code) are Used:

To move from State 5 to State 4

DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS

pOriginPoints to the application’s TW_IDENTITY structure. pDestPoints to the Source’s TW_IDENTITY structure.pDataPoints to a structure of type TW_USERINTERFACE. The definition of TW_USERINTERFACE is:

typedef struct { TW_BOOL ShowUI; TW_BOOL ModalUI; TW_HANDLE hParent; } TW_USERINTERFACE, FAR *pTW_USERINTERFACE;

Its contents are not used.

Note the following:


• If the Source’s User Interface was displayed: This operation causes the Source’s user interface, if displayed during the transition from State 4 to 5, to be lowered. This operation is sent by the application in response to a MSG_CLOSEDSREQ from the Source. This request from the Source appears in the TWMessage field of the TW_EVENT structure. It is sent back from the DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT operation used by the application to send events to the application.

• If the application did not have the Source’s User Interface displayed: The application invokes this command when all transfers have been completed. In addition, the application could invoke this operation to transition back to State 4 if it wanted to modify one or more of the capability settings before acquiring more data.


DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDS


pDestShould reference a NULL value (indicates destination is Source Manager)

pDataPoints to a structure of type TW_IDENTITYThis is the same TW_IDENTITY structure that you have used throughout the session to direct operation triplets to this Source.

When this operation is completed, the Source is closed. (In a more complicated scenario, if the application had more than one Source open, it must close them all before closing the Source Manager. Once all Sources are closed and the application does not plan to initiate any other TWAIN session with another Source, the Source Manager should be closed by the application.)


DG_CONTROL / DAT_PARENT / MSG_CLOSEDSM

pOriginPoints to the application’s TW_IDENTITY structure. pDestShould reference a NULL value (indicates destination is Source Manager)pDataTypically, you would expect to see this point to a structure of type TW_PARENT but this is not the case. This is an exception to the usual situation where the DAT field of the triplet identifies the data structure for pData.On Windows: pData points to the window handle (hWnd) that acted as the Source’s “parent”. The variable is of type TW_INT32. For 16 bit Microsoft Windows, the handle is stored in the low word of the 32 bit integer and the upper word is set to zero. If running under the WIN32 environment, this is a 32 bit window handle.On Macintosh: pData should be a 32-bit NULL value.

To Move from State 2 to State 1


Chapter 3

Once the Source Manager has been closed, the application must unload the DLL (on Windows) from memory before continuing.

On Windows:Use FreeLibrary( hDSMLib); where hDSMLib is the handle to the Source Manager DLL returned from the call to LoadLibrary( ) seen earlier (in the State 1 to 2 section).

On Macintosh:No action is necessary.

TWAIN Session Review

Applications have flexibility regarding which state they leave their TWAIN sessions in between TWAIN commands (such as Select Source and Acquire).

For example:

• An application might load the Source Manager on start-up and unload it on exit. Or, it might load the Source Manager only when it is needed (as indicated by Select Source and Acquire).

• An application might open a Source and leave it in State 4 between acquires.

The following is the simplest view of application’s TWAIN flow. All TWAIN actions are initiated by a TWAIN command, either user-initiated (Select Source and Acquire) or notification from the Source (MSG_XFERREADY and MSG_CLOSEDSREQ).

Application Receives

State Application Action

Select Source... 1 -> 22 -> 3

3 -> 22 -> 1

Load Source ManagerDG_CONTROL / DAT_PARENT / MSG_OPENDSMDG_CONTROL / DAT_IDENTITY / MSG_USERSELECTDG_CONTROL / DAT_PARENT / MSG_CLOSEDSMUnload Source Manager

Acquire... 1 -> 22 -> 33 -> 4

4 -> 5

Load Source ManagerDG_CONTROL / DAT_PARENT / MSG_OPENDSMDG_CONTROL / DAT_IDENTITY / MSG_OPENDSCapability NegotiationDG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS


Error HandlingYour application must be robust enough to recognize and handle error conditions that may occur during a TWAIN session. Every TWAIN operation triplet has a defined set of Return Codes and Conditions Codes that it may generate. These codes are listed on the reference pages for each triplet located in Chapter 7, "Operation Triplets.” Be sure to check the Return Code following every call to the DSM_Entry function. If it is TWRC_FAILURE, make sure your code checks the Condition Code and handles the error condition appropriately.

The following code segment illustrates the basic operations for doing this:

TW_STATUS twStatus;if (rc == TWRC_FAILURE) //check Condition Code rc = (*pDSM_Entry) (&AppID, &SourceID, DG_CONTROL, DAT_STATUS, MSG_GET, (TW_MEMREF)&twStatus); switch (twStatus.ConditionCode) //handle each possible Condition Code for the operation

Common Types of Error Conditions

Sequence Errors

The TWAIN protocol allows the invoking of specific operations only while the TWAIN session is in a particular state or states. The valid states for each operation are listed on the operation’s reference pages inChapter 7, "Operation Triplets.” If an operation is called from an

MSG_XFERREADY 6

6 -> 77 -> 66 -> 5

For each pending transfer: DG_IMAGE / DAT_IMAGEINFO / MSG_GET DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET DG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENT DG_IMAGE / DAT_IMAGExxxxXFER / MSG_GET DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERAutomatic transition to State 5 if TW_PENDINGXFERS.Count equals 0.

MSG_CLOSEDSREQ 5 -> 44 -> 33 -> 22 -> 1


DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDSDG_CONTROL / DAT_PARENT / MSG_CLOSEDSM

Unload the Source Manager

Application Receives

State Application Action


Chapter 3

inappropriate state, the call will return an error, TWRC_FAILURE, and set the Condition Code to TWCC_SEQERROR. Although this error should not occur if both the application and Source are behaving correctly, it is possible for the session to get out of sync.

If this error occurs, correct it by assuming the Source believes it is in State 7. The application should invoke the correct operations to back up from State 7 to State 6 and so on down the states until an operation succeeds. Then, the application can continue or terminate the session.

The following pseudo code illustrates this:

if (TWCC_SEQERROR)

// Assume State 7, start backing out from State 7 until

// the Condition Code != TWCC_SEQERROR

State 7 to 6 DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER

State 6 to 5 DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET

State 5 to 4 DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS

State 4 to 3 DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDS

Low Memory Errors

Another common type of error condition occurs when insufficient memory is available to perform a requested operation. The most likely times for this to occur are:

• When a Source is being opened

• When a Source is being enabled

• During a Native image transfer

Your application must check the Return Code and Condition Code (TWRC_FAILURE / TWCC_LOWMEMORY) to recognize this. Your application may be able to free up sufficient memory to continue or it must quit.

State Transition Operation Triplet Errors

Many operations normally cause state transitions. If one of these operations fails, for example, returns TWRC_FAILURE, do not make the state transition. The application must check the Return Code following every operation and update the current state only if the operation succeeds.

An implied state transition during DG_CONTROL/DAT_PENDINGXFERS/ MSG_ENDXFER deserves special note here. If the Count field of the TW_PENDINGXFERS structure is zero then the source will automatically transition back to State 5. Application writers should be aware of this condition and react accordingly.

Error Handling and State Transitions

It is possible that during execution of any triplet that the data source will fail unexpectedly. It is very important that applications pay attention to the TWAIN State of the data source at the time of failure. A hanging or deadlock condition will occur if the application fails to recover from error conditions with the proper state transitions. Most error handling is fairly obvious, however the following items have been mishandled in the past.


Failing Transition to State 5

A data source may fail a call to DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS unexpectedly. It is important to note that if an application requests the User Interface be suppressed, and the data source returns a code of TWRC_CHECKSTATUS, this means only that User Interface suppression was not possible. The transition to State 5 still occurred. If the application does not like this condition, then it may call MSG_DISABLEDS to close the data source without further user interaction. A return code of TWRC_FAILURE indicates that the transition to State 5 has not occurred.

Failure During State 6 or 7

It is important to be aware that when an error occurs during image transfer, a state transition to State 5 is not implicit. A call to DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET or MSG_ENDXFER is required for a state transition back to State 5. If an applications calls MSG_DISABLEDS immediately after such a failure without first making the required calls to DAT_PENDINGXFERS, the resulting behavior of the data source will not be predictable. The data source should fail any call to MSG_DISABLEDS outside of State 5.

Requirements for an Application to be TWAIN-CompliantApplications are required to support only a subset of the defined TWAIN operations. As an application advances its need to set attributes it will also need to implement a more complete set of the defined operations. This includes provision of support for more transfer mechanisms.

An application must support the following to be considered TWAIN-compliant:

Requirements

All TWAIN Applications must support the following:

Operations

The following six operations are consumed by the Source Manager:





DG_CONTROL / DAT_STATUS / MSG_GET

The following seven operations are consumed by a Source:






Chapter 3





Notices

Every application must support receipt of two notices from Sources. These are:

MSG_XFERREADY indicates application can initiate transfer

MSG_CLOSEDSREQ indicates the Source needs to be disabled

Capabilities

Applications must support one capability:

CAP_XFERCOUNT Application sets the maximum number of transfers a Source is allowed to offer per session.

Applications that consume image information should support negotiation with the following capabilities:

ICAP_XFERMECH the transfer mechanism to be used for the next transfer

ICAP_UNITS unit of measure for all measured values (default is inches)

ICAP_PIXELTYPE how image data is interpreted (Color, Gray, B&W, etc.)

Source requirements for TWAIN-compliance are presented in Chapter 5, "Source Implementation.”


4Advanced Application Implementation

Chapter ContentsCapabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-1Options for Transferring Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-17The ImageData and Its Layout. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-24Transfer of Multiple Images. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-27Transfer of Compressed Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-33Alternative User Interfaces. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-37Grayscale and Color Information for an Image . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-40Contrast, Brightness, and Shadow Values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-42

Using TWAIN to acquire a raster image from a device is relatively simple to implement as demonstrated in Chapter 3, "Application Implementation.” However, TWAIN also allows application developers to go beyond the simple acquisition of a single image in Native (DIB or PICT) format. These more advanced topics are discussed in this chapter.

CapabilitiesCapabilities, and the power of an application to negotiate capabilities with the Source, give control to TWAIN-compliant applications. In Chapter 4, "Advanced Application Implementation,” you saw the negotiation of one capability, CAP_XFERCOUNT. This capability was negotiated during State 4 as is always the case unless delayed negotiation is agreed to by both the application and Source. In fact, there is much more to know about capabilities.

Capability Values

Several values are used to define each capability. As seen in Chapter 10, "Capabilities,” TWAIN defines a Default Value and a set of Allowed Values for each of the capabilities. The application is not able to modify the Default Value. However, it is able to limit the values offered to a user to a subset of the Allowed Values and to select the capability’s Current Value.


Chapter 4

Default Value

When a Source is opened, the Current Values for each of its capabilities are set to the TWAIN Default Values listed inChapter 10, "Capabilities.” If no default is defined by TWAIN, the Source will select a value for its default. An application can return a capability to its TWAIN-defined default by issuing a DG_CONTROL / DAT_CAPABILITY / MSG_RESET operation.

Although TWAIN defines defaults for many of the capabilities, a Source may have a different value that it would prefer to use as its default because it would be more efficient. For example, the Source may normally use a 0 bit in a black and white image to indicate white. However, the default for ICAP_PIXELFLAVOR is TWPF_CHOCOLATE which states that a 0 represents black. Although the TWAIN default is TWPF_CHOCOLATE, the Source’s preferred default would be TWPF_VANILLA. When the application issues a DG_CONTROL / DAT_CAPABILITY / MSG_GETDEFAULT operation, the Source returns information about its preferred defaults. The Source and application may be able to negotiate a more efficient transfer based on this information.

Note that this does not imply that the TWAIN defaults should be completely disregarded. When trying to resolve the conflict between the “preferred” value of a particular data source capability and the TWAIN-specified default, it should be considered that the problem is similar to storing and restoring image attributes from session to session. It is reasonable to assume that a data source will want to store the current values for some capabilities to be restored as the current values in a future session. It is then also reasonable to expect that these restored values will be reflected as the current settings for the appropriate capabilities. While storing settings is only really useful for image attributes (the data source would not store the value of ICAP_PIXELFLAVOR, but it might store the current ICAP_RESOLUTION), it should be stated that preferred values of a data source are to be treated in the same manner.

At the time of loading the data source, all current values for the appropriate capabilities would be set to values that have either been restored from a previous session, or those that are “preferred” by the data source. This current value will remain until it has been explicitly changed by the calling application, or that application issues a MSG_RESET.

These are best illustrated using examples, since not all capabilities are suitable for preferred values, and most are not suitable to be stored and restored across multiple scanning sessions.

Example 1: Scan Parameters are stored in one session and restored in another

1. User configures the data source User Interface with the following parameters: 4x6 inch image in 24-bit at 200 DPI X and Y resolution

2. User selects “Scan” and data source signals application to transfer.

3. Application acquires the image successfully.

4. Application disables the data source.

5. Application inquires during State 4 the current values of Frame, Pixel Type, Bit Depth, and Resolution.

6. Data source reports to each inquiry the current values that were set by the user: 4x6 inch image in 24-bit at 200 DPI X and Y resolution.

7. Application closes the data source.

8. During close procedure, the data source stores the current Frame, Pixel Type, Bit Depth and Resolution.


9. Application opens data source.

10. During open procedure, the data source restores current Frame, Pixel Type, Bit Depth and Resolution.

11. Application inquires during State 4 the current values of Frame, Pixel Type, Bit Depth, and Resolution.

12. Data source reports to each inquiry the current values that were restored from previous session: 4x6 inch image in 24-bit at 200 DPI X and Y resolution in one session.

Example 2: Data Source represents the preferred Pixel Flavor without compromising TWAIN Defined Default value

1. Application opens data source for the first time

2. Application inquires during State 4 about the Default Pixel Flavor

3. Data source reports that the default pixel flavor is TWPF_CHOCOLATE. (See Chapter 10, "Capabilities.”)

4. Application inquires during State 4 about the current pixel flavor.

5. Data source reports that the current pixel flavor is TWPF_VANILLA (because this device returns data in that gender natively).

6. Application issues reset to current pixel flavor.

7. During reset operation, data source changes current value to TWPF_CHOCOLATE and prepares to invert data during transfer to accommodate the calling application request.

There is a condition where this logic falls apart. If the data source wants to return a TW_ENUMERATION to a MSG_GET request for a constrained capability, there is a chance that the Default value imposed by the TWAIN Specification (Chapter 10, "Capabilities”) will not exist within the constrained set of values. In this case, the application should consider the default value to be undefined. Common sense should dictate that the data source provide some default that is reasonable within the currently available set of values for safety (a bad index in a TW_ENUMERATION could be a disaster). When the default value is actually used (during MSG_RESET) the constraints shall be lifted, and the original default value will once again exist and be defined. (See next section on Constrained Capabilities about MSG_RESET) This is only a problem with a TW_ENUMERATION container, since it contains an index to the default.

Current Value

The application may request to set the Current Value of a capability. If the Source’s user interface is displayed, the Current Value should be reflected (perhaps by highlighting). If the application sets the Current Value, it will be used for the acquire and transfer unless the user or an automatic Source process changes it. The application can determine if changes were made by checking the Current Value during State 6.

To determine just the capability’s Current Value, use DG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENT. To determine both the Current Value and the Available Values, use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation. For example, you could do a MSG_GET on ICAP_PIXELTYPE and the Source might return a TW_ENUMERATION container containing TWPT_BW, TWPT_GRAY, and TWPT_RGB as Available Values.

To set the Current Value:


Chapter 4

Use DG_CONTROL / DAT_CAPABILITY / MSG_SET and one of the following containers:

• TWON_ONEVALUE: Place the desired value in TW_ONEVALUE.Item.

• TWON_ARRAY: Place only the desired items in TW_ARRAY.ItemList.These must be a subset of the items returned by the Source from a MSG_GET operation.

It is also possible to set Current Values using the TW_ENUMERATION and TW_RANGE containers. See the Available Values information for details.

Available Values

To limit the settings the Source can use during the acquire and transfer process, the application may be able to restrict the Available Values. The Source should not use a value outside these values. These restrictions should be reflected in the Source’s user interface so unavailable values are not offered to the user.

For example, if the MSG_GET operation on ICAP_PIXELTYPE indicates the Source supports TWPT_BW, TWPT_GRAY, and TWPT_RGB images and the application only wants black and white images, it can request to limit the Available Values to black and white.

To limit the Available Values:

Use DG_CONTROL / DAT_CAPABILITY / MSG_SET and one of the following containers:

• TWON_ENUMERATION: Place only the desired values in the TW_ENUMERATION.ItemList field. The Current Value can also be set at this time by setting the CurrentIndex to point to the desired value in the ItemList.

• TWON_RANGE: Place only the desired values in the TW_RANGE fields. The current value can also be set by setting the CurrentValue field.

Note: TW_ONEVALUE and TW_ARRAY containers cannot be used to limit the Available Values.

Capability Negotiation

The negotiation process consists of three basic parts:

1. The application determines which capabilities a Source supports

2. The application sets the supported capabilities as desired

3. The application verifies that the settings were accepted by the Source

Negotiation (Part 1)Application Determines Which Capabilities the Source Supports

Step 1Application allocates a TW_CAPABILITY structure and fills its fields as follows:

• Cap = the CAP_ or ICAP_ name for the capability it is interested in

• ConType = TWON_DONTCARE16

• hContainer = NULL


Step 2Application uses the TW_CAPABILITY structure in a DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.

Step 3The Source examines the Cap field to see if it supports the capability. If it does, it creates information for the application. In either case, it sets its Return Code appropriately.

Step 4Application examines the Return Code, and maybe the Condition Code, from the operation.If TWRC_SUCCESS then the Source does support the capability and

• The ConType field was filled by the Source with a container identifier (TWON_ARRAY, TWON_ENUMERATION, TWON_ONEVALUE, or TWON_RANGE)

• The Source allocated a container structure of ConType and referenced the hContainer field to this structure. It then filled the container with values describing the capability’s Current Value, Default Value, and Available Values.

Based on the type of container and its contents (whose type is indicated by it ItemType field), the application can read the values. The application must deallocate the container.If TWRC_FAILURE and TWCC_CAPUNSUPPORTED

• Source does not support this capability

The application can repeat this process for every capability it wants to learn about. If the application really only wants to get the Current Value for a capability, it can use the MSG_GETCURRENT operation instead. In that case, the ConType will just be TWON_ONEVALUE or TWON_ARRAY but not TWON_RANGE or TWON_ENUMERATION.

Note: The capability, CAP_SUPPORTEDCAPS, returns a list of capabilities that a Source supports. But it doesn’t indicate whether the supported capabilities can be negotiated, If the Source does not support the CAP_SUPPORTEDCAPS capabilities, it returns TWRC_FAILURE / TWCC_CAPUNSUPPORTED.

Negotiation (Part 2)The Application Sets the Supported Capability as Desired

Step 1

Application allocates a TW_CAPABILITY structure and fills its fields as follows:

• Cap = the CAP_ , ICAP_, or ACAP_name for the capability it is interested in

• ConType = TWON_ARRAY, TWON_ENUMERATION, TWON_ONEVALUE or TWON_RANGE (Refer to Chapter 10, "Capabilities” to see each capability and what type(s) of container may be used to set a particular capability.)

• hContainer = The application must allocate a structure of type ConType and reference this field to it. (See the next step.)

Step 2Application allocates a structure of type ConType and fills it. Based on values received from the Source during the MSG_GET, it can specify the desired Current Value and Available Values that it wants the Source to use. The application should not attempt to set


Chapter 4

the Source’s Default Value, just put an appropriate constant in that field (ex. TWON_DONTCARE32).

Note: The application is responsible for deallocating the container structure when the operation is finished.

Step 3 Send the request to the Source using DG_CONTROL / DAT_CAPABILITY / MSG_SET.

Negotiation (Part 3)The Application MUST Verify the Result of Their Request

Step 1Even if a Source supports a particular capability, it is not required to support the setting of that capability. The application must examine the Return Code from the MSG_SET request to see what took place.If TWRC_SUCCESS then the Source set the capability as requested.If TWRC_CHECKSTATUS then

• The Source could not use one or more of your exact values. For instance, you asked for a value of 310 but it could only accept 100, 200, 300, or 400. Your request was within its legitimate range so it rounded it to its closest valid setting.


Use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation to determine the current and available settings at this time. This is the only way to determine if the Source’s choice was acceptable to your application.If TWRC_FAILURE / TWCC_BADVALUE then

• Either the Source is not granting your request to set or restrict the value.

• Or, your requested values were not within its range of legitimate values. It may have attempted to set the value to its closest available value.

Use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation to determine the current and available settings at this time. This is the only way to determine if your application can continue without your requested values.

You can repeat the setting and verifying processes for every capability of interest to your application. Remember, your application must deallocate all container structures.

The Most Common Capabilities

TWAIN defines over 150 capabilities. Although the number may seem overwhelming, it is easier to handle if you recognize that some of the capabilities are more commonly used. Here are some of these capabilities:

Basic Capabilities

UnitsThe ICAP_UNITS capability determines the unit of measure which will be used by the Source. The default is inches but centimeters, pixels, etc. are allowed. This capability’s value is used when measuring several other values in capabilities and data structures including: ICAP_PHYSICALHEIGHT, ICAP_PHYSICALWIDTH, ICAP_XNATIVERESOLUTION,ICAP_YNATIVERESOLUTION, ICAP_XRESOLUTION, ICAP_YRESOLUTION, TW_FRAME, TW_IMAGEINFO.XResolution, TW_IMAGEINFO.YResolution

Sense of the PixelThe ICAP_PIXELFLAVOR specifies how a bit of data should be interpreted when transferred from Source to application. The default is TWPF_CHOCOLATE which means a 0 indicates black (or the darkest color). The alternative, TWPF_VANILLA, means a 0 indicates white (or the lightest color).

ResolutionThe image resolution is reported in the TW_IMAGEINFO structure. To inquire or set the Source’s resolution, use ICAP_XRESOLUTION and ICAP_YRESOLUTION.Refer also to ICAP_XNATIVERESOLUTION and ICAP_YNATIVERESOLUTION.


Chapter 4

Image Type Capabilities

Types of PixelThe application should negotiate ICAP_PIXELTYPE and ICAP_BITDEPTH unless it can handle all pixel types at all bit depths. The allowed pixel types are: TWPT_BW, TWPT_GRAY, TWPT_RGB, TWPT_PALETTE, TWPT_CMY, TWPT_CMYK, TWPT_YUV, TWPT_YUVK, TWPT_CIEXYZ, and TWPT_INFRARED.

Depth of the Pixels (in bits) A pixel type such as TWPT_BW allows only 1 bit per pixel (either black or white). The other pixel types may allow a variety of bits per pixel (4-bit or 8-bit gray, 8-bit or 24-bit color). Be sure to set the ICAP_PIXELTYPE first, then set the ICAP_BITDEPTH.

Parameters for Acquiring the Image

ExposureSeveral capabilities can influence this. They include ICAP_BRIGHTNESS, ICAP_CONTRAST, ICAP_SHADOW, ICAP_HIGHLIGHT, ICAP_GAMMA, and ICAP_AUTOBRIGHT.

ScalingTo instruct a Source to scale an image before transfer, refer to ICAP_XSCALING and ICAP_YSCALING.

RotationTo instruct a Source to rotate the image before transfer, refer to ICAP_ROTATION and ICAP_ORIENTATION.

Constrained Capabilities and Message Responses

There is some confusion about how the data source should respond to various capability queries when the application has imposed constraints upon the supported values. The following guidelines should help clarify the situation.

MSG_RESET

It is known that this call resets the current value of the requested capability to the default. It must also be stated that this call will also reset any application imposed constraints upon the requested capability.

MSG_GETCURRENT, and MSG_GETDEFAULT

It is intuitive to assume that this message should not be supported by capabilities that have no Current or Default value. However, the specification says otherwise in Chapter 10, "Capabilities” (a good example is ICAP_SUPPORTEDCAPS). In this case, it makes sense to simply respond to these messages in the same manner as MSG_GET.

It can also be assumed that it is more intuitive for a data source to respond to this capability with a TW_ONEVALUE container in all cases that a TW_ONEVALUE container is allowed.

MSG_GET

If an application has constrained the current capability, then the data source response to this message should reflect those constraints. Otherwise, this should respond with all the values


that the data source supports. Of course, the number of values that can be placed in the response are restricted by the allowed containers for the particular current capability outlined in Chapter 10, "Capabilities.”

MSG_SET

As indicated in Chapter 7, "Operation Triplets,” description of this capability triplet:

“Current Values are set when the container is a TW_ONEVALUE or TW_ARRAY. Available and Current Values are set when the container is a TW_ENUMERATION or TW_RANGE.”

To further clarify this operation, it should be stated that when an application imposes a constraint, the data source must consider the set of supported values and the set of requested constraints. The resulting set of values shall contain only the values that are shared by those supported and those requested.

A condition may arise after constraints are imposed, where the default value is no longer within the set of supported values. When using a TW_ENUMERATION, the reported default index should be changed by the data source to something that falls within the new constrained set. This is simply a precaution to ensure it is a valid index. In this case, the Default index in a TW_ENUMERATION loses meaning and should be ignored by applications, since MSG_RESET shall cause the constraints to be eliminated.

Capability Containers in Code Form

Capability information is passed between application and Source by using data structures called containers: TW_ARRAY, TW_ENUMERATION, TW_ONEVALUE, and TW_RANGE. The actions needed to create (pack) and read (unpack) containers are illustrated here in the following code segments. Containers are flexible in that they can be defined to contain one of many types of data. Only one ItemType (TWTY_xxxx) is illustrated per Container (TWON_xxxx) here. Refer to the toolkit disk for complete packing and unpacking utilities that you can use with containers.

Reading (unpacking) a Container from a MSG_GET Operation

//-------------------------------------------------

//Example of DG_CONTROL / DAT_CAPABILITY / MSG_GET

//-------------------------------------------------

TW_CAPABILITY twCapability;

TW_INT16 rc;

//Setup TW_CAPABILITY Structure

twCapability.Cap = Cap; //Fill in capability of interest

twCapability.ConType = TWON_DONTCARE16;

twCapability.hContainer = NULL;

//Send the Triplet

rc = (*pDSM_Entry)(&AppID,

&SourceID,

DG_CONTROL,

DAT_CAPABILITY,


Chapter 4

MSG_GET,

(TW_MEMREF)&twCapability);

//Check return code

if (rc == TWRC_SUCCESS)

{

//Switch on Container Type

switch (twCapability.ConType)

{

//-----ENUMERATION

case TWON_ENUMERATION:

{

pTW_ENUMERATION pvalEnum;

TW_UINT16 valueU16;

TW_UINT16 index;

pvalEnum = (pTW_ENUMERATION)GlobalLock(twCapability.hContainer);

NumItems = pvalEnum->NumItems;

CurrentIndex = pvalEnum->CurrentIndex;

DefaultIndex = pvalEnum->DefaultIndex;

for (index = 0; index < pvalEnum->NumItems; index++)

{

if (pvalEnum->ItemType == TWTY_UINT16)

{

valueU16 = ((TW_UINT16)(pvalEnum->ItemList[index*2]));

//Store Item Value

}

else if (pvalOneValue->ItemType == TWTY_BOOL)

{

valueBool = ((TW_BOOL*)&pvalEnum->ItemList)[index];

//Store Item Value

}

}

GlobalUnlock(twCapability.hContainer);

}

break;


//-----ONEVALUE

case TWON_ONEVALUE:

{

pTW_ONEVALUE pvalOneValue;

TW_BOOL valueBool;

pvalOneValue = (pTW_ONEVALUE)GlobalLock(twCapability.hContainer);

if (pvalOneValue->ItemType == TWTY_BOOL)

{

valueBool = (TW_BOOL)pvalOneValue->Item;

//Store Item Value

}


}

break;

//-----RANGE

case TWON_RANGE:

{

pTW_RANGE pvalRange;

pTW_FIX32 pTWFix32;

float valueF32;

TW_UINT16 index;

pvalRange = (pTW_RANGE)GlobalLock(twCapability.hContainer);

if ((TW_UINT16)pvalRange->ItemType == TWTY_FIX32)

{

pTWFix32 = &(pvalRange->MinValue);

valueF32 = FIX32ToFloat(*pTWFix32);

//Store Item Value

pTWFix32 = &(pvalRange->MaxValue);


//Store Item Value

pTWFix32 = &(pvalRange->StepSize);


//Store Item Value

}



Chapter 4

}

break;

//-----ARRAY

case TWON_ARRAY:

{

pTW_ARRAY pvalArray;

TW_UINT16 valueU16;

TW_UINT16 index;

pvalArray = (pTW_ARRAY)GlobalLock(twCapability.hContainer);

for (index = 0; index < pvalArray->NumItems; index++)

{

if (pvalArray->ItemType == TWTY_UINT16)

{

valueU16 = ((TW_UINT16)(pvalArray->ItemList[index*2]));

//Store Item Value

}

}


}

break;

} //End Switch Statement

GlobalFree(twCapability.hContainer);

} else {

//Capability MSG_GET Failed check Condition Code

}

/**********************************************************

* Fix32ToFloat

* Convert a FIX32 value into a floating point value.

**********************************************************/

float FIX32ToFloat (TW_FIX32 fix32)

{

float floater;

floater = (float)fix32.Whole + (float)fix32.Frac / 65536.0; return floater;

}


Creating (packing) a Container for a MSG_SET Operation

//-------------------------------------------------

//Example of DG_CONTROL / DAT_CAPABILITY / MSG_SET

//-------------------------------------------------

TW_CAPABILITY twCapability;

TW_INT16 rc;

TW_UINT32 NumberOfItems;

twCapability.Cap = Cap; //Insert Capability of Interest

twCapability.ConType = Container;

//Use TWON_ONEVALUE or TWON_ARRAY to set current value

//Use TWON_ENUMERATION or TWON_RANGE to limit available values

switch (twCapability.ConType)

{

//-----ENUMERATION

case TWON_ENUMERATION:

{

pTW_ENUMERATION pvalEnum;

//The number of Items in the ItemList

NumberOfItems = 2;

//Allocate memory for the container and additional ItemList

// entries

twCapability.hContainer = GlobalAlloc(GHND, (sizeof(TW_ENUMERATION) + sizeof(TW_UINT16) * (NumberOfItems)));

pvalEnum = (pTW_ENUMERATION)GlobalLock(twCapability.hContainer);

pvalEnum->NumItems = 2 //Number of Items in ItemList

pvalEnum->ItemType = TWTY_UINT16;

((TW_UINT16)(pvalEnum->ItemList[0])) = 1;

((TW_UINT16)(pvalEnum->ItemList[1])) = 2;


}

break;

//-----ONEVALUE

case TWON_ONEVALUE:

{


Chapter 4

pTW_ONEVALUE pvalOneValue;

twCapability.hContainer = GlobalAlloc(GHND, sizeof(TW_ONEVALUE));

pvalOneValue = (pTW_ONEVALUE)GlobalLock(twCapability.hContainer);

(TW_UINT16)pvalOneValue->ItemType = TWTY_UINT16;

(TW_UINT16)pvalOneValue->Item = 1;


}

break;

//-----RANGE

case TWON_RANGE:

{

pTW_RANGE pvalRange;

TW_FIX32 TWFix32;

float valueF32;

twCapability.hContainer = GlobalAlloc(GHND, sizeof(TW_RANGE));

pvalRange = (pTW_RANGE)GlobalLock(twCapability.hContainer);

(TW_UINT16)pvalRange->ItemType = TWTY_FIX32;

valueF32 = 100;

TWFix32 = FloatToFIX32 (valueF32);

pvalRange->MinValue = *((pTW_INT32) &TWFix32);

valueF32 = 200;

TWFix32 = FloatToFIX32 (valueF32);

pvalRange->MaxValue = *((pTW_INT32) &TWFix32);


}

break;

//-----ARRAY

case TWON_ARRAY:

{

pTW_ARRAY pvalArray;

//The number of Items in the ItemList

NumberOfItems = 2;

//Allocate memory for the container and additional ItemList entries


twCapability.hContainer = GlobalAlloc(GHND, (sizeof(TW_ARRAY) + sizeof(TW_UINT16) * (NumberOfItems)));

pvalArray = (pTW_ARRAY)GlobalLock(twCapability.hContainer);

(TW_UINT16)pvalArray->ItemType = TWTY_UINT16; (TW_UINT16)pvalArray->NumItems = 2; ((TW_UINT16)(pvalArray->ItemList[0])) = 1; ((TW_UINT16)(pvalArray->ItemList[1])) = 2;


}

break;

}

//-----MSG_SET

rc = (*pDSM_Entry)(&AppID,

&SourceID,

DG_CONTROL,

DAT_CAPABILITY,

MSG_SET,

(TW_MEMREF)&twCapability);

GlobalFree(twCapability.hContainer);

switch (rc)

{

case TWRC_SUCCESS:

//Capability's Current or Available value was set as specified

case TWRC_CHECKSTATUS:

//The Source matched the specified value(s) as closely as possible

//Do a MSG_GET to determine the settings made

case TWRC_FAILURE:

//Check the Condition Code for more information

}

/**********************************************************

* FloatToFix32

* Convert a floating point value into a FIX32.

**********************************************************/

TW_FIX32 FloatToFix32 (float floater)

{

TW_FIX32 Fix32_value;


Chapter 4

TW_INT32 value = (TW_INT32) (floater * 65536.0 + 0.5);

Fix32_value.Whole = value >> 16;

Fix32_value.Frac = value & 0x0000ffffL;

return (Fix32_value);

}

Delayed Negotiation - Negotiating Capabilities After State 4

Applications may inquire about a Source’s capability values at any time during the session with the Source. However, as a rule, applications can only request to set a capability during State 4. The rationale behind this restriction is tied to the display of the Source’s user interface when the Source is enabled. Many Sources will modify the contents of their user interface in response to some of the application’s requested settings. These user interface modifications prevent the user from selecting choices that do not meet the application’s requested values. The Source’s user interface is never displayed in State 4 so changes can be made without the user’s awareness. However, the interface may be displayed in States 5 through 7.

Some capabilities have no impact on the Source’s user interface and the application may really want to set them later than State 4. To allow delayed negotiation, the application must request, during State 4, that a particular capability be able to be set later (during States 5 or 6). The Source may agree to this request or deny it. The request is negotiated by the application with the Source by using the DG_CONTROL / DAT_CAPABILITY operations on the CAP_EXTENDEDCAPS capability.

On the CAP_EXTENDEDCAPS capability, the DG_CONTROL / DAT_CAPABILITY operations:

MSG_GET

Indicates all capabilities that the Source is willing to negotiate in State 5 or 6.

MSG_SET

Specifies which capabilities the application wishes to negotiate in States 5 or 6.

MSG_GETCURRENT Provides a list of all capabilities which the Source and application have agreed to allow to be negotiated in States 5 or 6.

As with any other capability, if the Source does not support negotiating CAP_EXTENDEDCAPS, it will return the Return Code TWRC_FAILURE with the Condition Code TWCC_CAPUNSUPPORTED.

If an application attempts to set a capability in State 5 or 6 and the Source has not previously agreed to this arrangement, the operation will fail with a Return Code of TWRC_FAILURE and a Condition Code of TWCC_SEQERROR.

If an application does not use the Source’s user interface but presents its own, the application controls the state of the Source explicitly. If the application wants to set the value of any capability, it returns the Source to State 4 and does so. Therefore, an application using its own user interface will probably not need to use CAP_EXTENDEDCAPS.


Options for Transferring DataAs discussed previously, there are three modes defined by TWAIN for transferring data:

• Native

• Disk File

• Buffered Memory

A Source is required to support Native and Buffered Memory transfers.

Native Mode Transfer

The use of Native mode, the default mode, for transferring data was covered in Chapter 3, "Application Implementation.” There is one potential limitation that can occur in a Native mode transfer. That is, there may not be an adequately large block of RAM available to hold the image. This situation will not be discovered until the transfer is attempted when the application issues the DG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET operation.

When the lack of memory appears, the Source may respond in one of several ways. It can:

• Simply fail the operation.

• Clip the image to make it fit in the available RAM - The Source should notify the user that the clipping operation is taking place due to limited RAM. The clipping should maintain both the aspect ratio of the selected image and the origin (upper-left).

• Interact with the user to allow them to resize the image or cancel the capture.

The Return Code / Condition Code returned from the DG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET operation may indicate one of these actions occurred.

If the Return Code is TWRC_XFERDONE:

This indicates the transfer was completed and the session is in State 7. However, it does not guarantee that the Source did not clip the image to make it fit. Even if the application issued a DG_IMAGE / DAT_IMAGEINFO / MSG_GET operation prior to the transfer to determine the image size, it cannot assume that the ImageWidth and ImageLength values returned from that operation really apply to the image that was ultimately transferred. If the dimensions of the image are important to the application, the application should always check the actual transferred image size after the transfer is completed. To do this:

1. Execute a DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation to move the session from State 7 to State 6 (or 5).

2. Determine the actual size of the image that was transferred:

a. On Windows - Read the DIB header

b. On Macintosh - Check the picFrame in the Picture


Chapter 4

If the Return Code is TWRC_CANCEL:

The acquisition was canceled by the user. The session is in State 7. Execute a DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation to move the session from State 7 to State 6 (or 5).

If the Return Code is TWRC_FAILURE:

Check the Condition Code to determine the cause of the failure. The session is in State 6. No memory was allocated for the DIB or PICT. The image is still pending. If lack of memory was the cause, you can try to free additional memory or discard the pending image by executing DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER.

Disk File Mode Transfer

Beginning with version 1.9, there are now two file transfer mechanisms available. Windows developers may continue to use the TWSX_FILE option. Macintosh developers must use TWSX_FILE2, instead of TWSX_FILE, in order to correctly address image and audio files in the newer versions of the operating system.

Determine if a Source Supports the Disk File Mode

• Use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.

• Set the TW_CAPABILITY’s Cap field to ICAP_XFERMECH.

• The Source returns information about the transfer modes it supports in the container structure pointed to by the hContainer field of the TW_CAPABILITY structure. The disk file mode is identified as TWSX_FILE or TWSX_FILE2. Sources are not required to support Disk File Transfer so it is important to verify its support.

After Verifying Disk File Transfer is Supported, Set Up the Transfer

During State 4:

• Set the ICAP_XFERMECH to TWSX_FILE or TWSX_FILE2. Use the DG_CONTROL / DAT_CAPABILITY / MSG_SET operation.

• Use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation to determine which file formats the Source can support. Set TW_CAPABILITY. Cap to ICAP_IMAGEFILEFORMAT and execute the MSG_GET. The Source returns the supported format identifiers which start with TWFF_ and may include TWFF_PICT, TWFF_BMP, TWFF_TIFF, etc. They are listed in the TWAIN.H file and in the Constants section of Chapter 8, "Data Types and Data Structures.”

During States 4, 5, or 6:To set up the transfer the DG_CONTROL / DAT_SETUPFILEXFER operation of MSG_GET, MSG_GETDEFAULT, and MSG_SET can be used.The data structure used in the DSM_Entry call is a TW_SETUPFILEXFER structure (for DAT_SETUPFILEXFER, on Windows and pre-1.9 Macintosh Sources and Applications):

typedef struct { TW_STR255 FileName; /* File to contain data */ TW_UINT16 Format; /* A TWFF_xxxx constant */ TW_HANDLE VrefNum; /* Used for Macintosh only */ } TW_SETUPFILEXFER, FAR *pTW_SETUPFILEXFER;


The application could use the MSG_GETDEFAULT operation to determine the default file format and filename (TWAIN.TMP or TWAIN.AUD in the current directory). If acceptable, the application could just use that file. However, most applications prefer to set their own values for filename and format. The MSG_SET operation allows this. It is done during State 6. To set your own filename and format, do the following:

1. Allocate the required TW_SETUPFILEXFER structure. Then, fill in the appropriate fields:

a. FileName – the desired filename. On Windows, be sure to include the complete path name.

b. Format – the constant for the desired, and supported, format (TWFF_xxxx). If you set it to an unsupported format, the operation returns TWRC_FAILURE / TWCC_BADVALUE and the Source resets itself to write data to the default file.

c. VRefNum – On Macintosh, write the file’s volume reference number. On Windows, fill in the field with a TWON_DONTCARE16.

2. Invoke the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET as appropriate.

Execute the Transfer into the File

After the application receives the MSG_XFERREADY notice from the Source and has issued the DG_CONTROL / DAT_SETUPFILEXFER / MSG_GET.

Use the following operation: DG_IMAGE / DAT_IMAGEFILEXFER / MSG_GET

This operation does not have an associated data structure but just uses NULL for the pData parameter in the DSM_Entry call.

• If the application has not specified a filename (during the setup) - the Source will use either its default file or the last file information it was given.

• If the file specified by the application does not exist - the Source should create it.

• If the file exists but already has data in it - the Source should overwrite the existing data. Notice, if you are transferring multiple files and using the same file name each time, you will overwrite the data unless you copy it to a different filename between transfers.

Note: The application cannot abort a Disk File transfer once initiated. However, the Source’s user interface may allow the user to cancel the transfer.

Following execution, be sure to check the Return Code:

TWRC_XFERDONE: File was written successfully. The application needs to invoke the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER to transition the session back to State 6 (or 5) as was illustrated in Chapter 4, "Advanced Application Implementation.”

TWRC_CANCEL: The user canceled the transfer. The contents of the file are undefined. Invoke DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER to transition the session back to State 6 (or 5) as was illustrated in Chapter 3, "Application Implementation.”


Chapter 4

TWRC_FAILUREThe Source remained in State 6.The contents of the file are undefined.The image is still pending. To discard it, use DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER.

Check the Condition Code to determine the cause of the failures. The alternatives are:

TWCC_BADDEST = Operation aimed at invalid Source

TWCC_OPERATIONERROR = Either the file existed but could not be accessed or a system error occurred during the writing

TWCC_SEQERROR = Operation invoked in invalid state (i.e. not 6)

Buffered Memory Mode Transfer

Set Capability Values for the Buffered Memory Mode, if Desired

Data is typically transferred in uncompressed format. However, if you are interested in knowing if the Source can transfer compressed data when using the buffered memory mode, perform a DG_CONTROL / DAT_CAPABILITY / MSG_GET on the ICAP_COMPRESSION. The values will include TWCP_NONE (the default) and perhaps others such as TWCP_PACKBITS, TWCP_JPEG ,etc. (See the list in the Constants section of Chapter 8, "Data Types and Data Structures.”) More information on compression is available later in this chapter in the section called Transfer of Compressed Data.

Set up the Transfer

During State 4:Set the ICAP_XFERMECH to TWSX_MEMORY by using the DG_CONTROL / DAT_CAPABILITY / MSG_SET operation.

During States 4, 5, or 6:The DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation is used by the application to determine what buffer sizes the Source wants to use during the transfer. The Source might have more accurate information in State 6.The data structure used in the DSM_Entry call is a TW_SETUPMEMXFER structure:

typedef struct {

TW_UINT32 MinBufSize /* Minimum buffer size in bytes */

TW_UINT32 MaxBufSize /* Maximum buffer size in bytes */

TW_UINT32 Preferred /* Preferred buffer size in bytes */

} TW_SETUPMEMXFER, FAR *pTW_SETUPMEMXFER;

The Source will fill in the appropriate values for its device.

Buffers Used for Uncompressed Strip Transfers

• The application is responsible for allocating and deallocating all memory used during the buffered memory transfer.

• For optimal performance, create buffers of the Preferred size.


• In all cases, the size of the allocated buffers must be within the limits of MinBufSize to MaxBufSize. If outside of these limits, the Source will fail the transfer operation with a Return Code of TWRC_FAILURE / TWCC_BADVALUE.

• If using more than one buffer, all buffers must be the same size.

• Raster lines must be double-word aligned and padded with zeros is recommended .

Execute the Transfer Using Buffers

After the application receives the MSG_XFERREADY notice from the Source and has issued the DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation:

• Allocate one or more buffers of the same size. The best size is the one indicated by the TW_SETUPMEMXFER.Preferred field. If that is impossible, be certain the buffer size is between MinBufSize and MaxBufSize.

• Allocate the TW_IMAGEMEMXFER structure. It will be used in the DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation.


Chapter 4

The TW_IMAGEMEMXFER structure looks like this:

typedef struct {

TW_UINT16 Compression; TW_UINT32 BytesPerRow; TW_UINT32 Columns; TW_UINT32 Rows; TW_UINT32 XOffset; TW_UINT32 YOffset; TW_UINT32 BytesWritten; TW_MEMORY Memory; } TW_IMAGEMEMXFER, FAR *pTW_IMAGEMEMXFER;

Fill in the TW_IMAGEMEMXFER’s first field with TWON_DONTCARE16 and the following six fields with TWON_DONTCARE32.

The TW_MEMORY structure embedded in there looks like this:

typedef struct {

TW_UINT32 Flags; TW_UINT32 Length; TW_MEMREF TheMem;

} TW_MEMORY, FAR *pTW_MEMORY;

Fill in the TW_MEMORY structure as follows:

Memory.Flags Place TWMF_APPOWNS bit-wise ORed with TWMF_POINTER or TWMF_HANDLE

Memory.Length The size of the buffer in bytes

Memory.TheMemA handle or pointer to the memory buffer allocated above (depending on which onewas specified in the Flags field).

Following each buffer transfer, the Source will have filled in all the fields except Memory which it uses as a reference to the memory block for the data.

The flow of the transfer of buffers is as follows:

Step 1Buffered Memory transfers provide no embedded header information. Therefore, the application must determine the image attributes. After receiving the MSG_XFERREADY, i.e. while in State 6, the application issues the DG_IMAGE / DAT_IMAGEINFO / MSG_GET and DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET operations to learn about the image’s bitmap characteristics and the size and location of the original image on the original page (before scaling or other processing). If additional information is desired, use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.


Step 2The application issues DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET.

Step 3The application checks the Return Code.

• If TWRC_SUCCESS:Examine the TW_IMAGEMEMXFER structure for information about the buffer. If you plan to reuse the buffer, copy the data to another location.Loop back to Step 2 to get another buffer. Be sure to reinitialize the information in the TW_IMAGEMEMXFER structure (including the Memory fields), if necessary. Issue another DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation.

• If TWRC_XFERDONE:This is how the Source indicates it just transferred the last buffer successfully. Examine the TW_IMAGEMEMXFER structure for information about the buffer. Perhaps, copy the data to another location, as desired, then go to Step 4.

• If TWRC_CANCEL:The user aborted the transfer. The application must send a DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER as described in Chapter 3, "Application Implementation” to move from State 7 to State 6 (or 5).

• If TWRC_FAILURE:Examine the Condition Code to determine the cause and handle it.If the failure occurred during the transfer of the first buffer, the session is in State 6. If the failure occurred on a subsequent buffer, the session is in State 7.The contents of the buffer are invalid and the transfer of the buffer is still pending. To abort it, use DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER.

Step 4Once the TWRC_XFERDONE has been returned, the application must send the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER to conclude the transfer. This was described in Chapter 3, "Application Implementation” in the section called State 7 to 6 to 5 - Conclude the Transfer.

Note: The majority of Sources divide the image data into strips when using buffered transfers. A strip is a horizontal band starting at the leftmost side of the image and spanning the entire width but covering just a portion of the image length. The application can verify that strips are being used if the information returned from the Source in the TW_IMAGEMEMXFER structure’s XOffset field is zero and the Columns field is equal to the value in the TW_IMAGEINFO structure’s ImageWidth field.

An alternative to strips is the use of tiles although they are used by very few Sources. Refer to the TW_IMAGEMEMXFER information in Chapter 8, "Data Types and Data Structures” for an illustration of tiles.

Buffered Memory Mode Transfer With File Format

This operation works very much like Buffered Memory Mode, but the data transferred from the Source to the Application conforms to the image file format specified by a previous call to DG_IMAGE / DAT_SETUPFILEXFER / MSG_GET. There is no requirement for the data to be


Chapter 4

transferred as complete image lines or for any kind of padding, the data is assumed to be self-contained and self-describing.

The ImageData and Its LayoutThe image which is transferred from the Source to the application has several attributes. Some attributes describe the size of the image. Some describe where the image was located on the original page. Still others might describe information such as resolution or number of bits per pixel. TWAIN provides means for the application to learn about these attributes.

Users are often able to select and modify an image’s attributes through the Source’s user interface. Additionally, TWAIN provides capabilities and operations that allow the application to impact these attributes prior to acquisition and transfer.

Getting Information About the Image That will be Transferred

Before the transfer occurs, while in State 6, the Source can provide information to the application about the actual image that it is about to transfer. Note, the information is lost once the transfer takes place so the application should save it, if needed. This information can be retrieved through two operations:

• DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET

• DG_IMAGE / DAT_IMAGEINFO / MSG_GET

The area of an image to be acquired will always be a rectangle called a frame. There may be one or more frames located on a page. Frames can be selected by the user or designated by the application. The TW_IMAGELAYOUT structure communicates where the image was located on the original page relative to the origin of the page. It also indicates, in its FrameNumber field, if this is the first frame, or a later frame, to be acquired from the page.

The TW_IMAGELAYOUT structure looks like this:

typedef struct { TW_FRAME Frame; TW_UINT32 DocumentNumber; TW_UINT32 PageNumber; TW_UINT32 FrameNumber; } TW_IMAGELAYOUT, FAR *pTW_IMAGELAYOUT;

The TW_FRAME structure specifies the values for the Left, Right, Top, and Bottom of the frame to be acquired. Values are given in ICAP_UNITS.


Figure 4-1. TW_FRAME Structure

The DG_IMAGE / DAT_IMAGEINFO / MSG_GET operation communicates other attributes of the image being transferred. The TW_IMAGEINFO structure looks like this:

typedef struct { TW_FIX32 XResolution; TW_FIX32 YResolution; TW_INT32 ImageWidth; TW_INT32 ImageLength; TW_INT16 SamplesPerPixel; TW_INT16 BitsPerSample[8]; TW_INT16 BitsPerPixel; TW_BOOL Planar; TW_INT16 PixelType; TW_UINT16 Compression; } TW_IMAGEINFO, FAR * pTW_IMAGEINFO;

Notice how the ImageWidth and ImageLength relate to the frame described by the TW_IMAGELAYOUT structure.

Changing the Image Attributes

Normally, the user will select the desired attributes. However, the application may wish to do this initially during State 4. For example, if the user interface will not be displayed, the application may wish to select the frame. The application can use a DG_IMAGE / DAT_IMAGELAYOUT / MSG_SET operation to define the area (frame) to be acquired. Although, there is no corresponding DG_IMAGE / DAT_IMAGEINFO / MSG_SET operation, the application can change those attributes by setting capabilities and the TW_IMAGELAYOUT data structure.

Here are the relationships:

TW_IMAGEINFO fields Capability or data structure that impacts the attribute

XResolution ICAP_XRESOLUTION

YResolution ICAP_YRESOLUTION

ImageWidth TW_IMAGELAYOUT.TW_FRAME.Right - TW_FRAME.Left **


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**ImageWidth and ImageLength are actually provided in pixels whereas TW_FRAME uses ICAP_UNITS.

Resolving Conflict Between ICAP_FRAMES, ICAP_SUPPORTEDSIZES, DAT_IMAGELAYOUT

Since there are several ways to negotiate the scan area, it becomes confusing when deciding what should take precedence. It is logical to assume that the last method used to set the frame will dictate the current frame. However, it may still be confusing to decide how that is represented during a MSG_GET operation for any of the three methods. The following behavior is suggested.

Note: Frame extents are only limited by ICAP_PHYSICALWIDTH and ICAP_PHYSICALHEIGHT. Setting ICAP_SUPPORTEDSIZES does NOT imply a new extent limitation. TWSS_xxxx sizes are simply predefined fixed frame sizes.

• If the frame is set in DAT_IMAGELAYOUT

• ICAP_FRAMES shall respond to MSG_GETCURRENT with the dimensions of the frame set in the DAT_IMAGELAYOUT call.

• ICAP_SUPPORTEDSIZES shall respond to MSG_GETCURRENT with TWSS_NONE

• If the current frame is set from ICAP_FRAMES

• DAT_IMAGELAYOUT shall respond with the dimensions of the current frame set in ICAP_FRAMES

• ICAP_SUPPORTEDSIZES shall respond to MSG_GETCURRENT with TWSS_NONE

• If the current fixed frame is set from ICAP_SUPPORTEDSIZES

• DAT_IMAGELAYOUT shall respond to MSG_GET with the dimensions of the fixed frame specified in ICAP_SUPPORTEDSIZES

• ICAP_FRAMES shall respond to MSG_GETCURRENT with the dimensions of the fixed frame specified in ICAP_SUPPORTEDSIZES

ICAP_ROTATION, ICAP_ORIENTATION Affect on ICAP_FRAMES, DAT_IMAGELAYOUT, DAT_IMAGEINFO

There is considerable confusion when trying to resolve the affect of Rotation and Orientation on the current frames and image layout. After careful consideration of the specification it has been

ImageLength TW_IMAGELAYOUT.TW_FRAME.Bottom - TW_FRAME.Top **

SamplesPerPixel ICAP_PIXELTYPE (i.e. TWPT_BW has 1, TWPT_RGB has 3)

BitsPerSample Calculated by BitsPerPixel divided by SamplesPerPixel

BitsPerPixel ICAP_BITDEPTH

Planar ICAP_PLANARCHUNKY

PixelType ICAP_PIXELTYPE

Compression ICAP_COMPRESSION

TW_IMAGEINFO fields Capability or data structure that impacts the attribute


concluded that ICAP_ROTATION and ICAP_ORIENTATION shall be applied after considering ICAP_FRAMES and DAT_IMAGELAYOUT.

Obviously a change in orientation will have an effect on the output image dimensions, so these must be reflected in DAT_IMAGEINFO during State 6. The resulting image dimensions shall be reported by the data source after considering the affect of the rotation on the current frame.

ICAP_ORIENTATION and ICAP_ROTATION are additive. The original frame is modified by ICAP_ORIENTATION as it is downloaded to the device by the Source, and represents the orientation of the paper being scanned. ICAP_ROTATION is then applied to the captured image to yield the final framing information that is reported to the Application in State 6 or 7. One possible reason for combining these two values is to use them to cancel each other out. For instance, some scanners with automatic document feeders may receive a performance benefit from describing an ICAP_ORIENTATION of TWOR_LANDSCAPE in combination with an ICAP_ROTATION of 90 degrees. This would allow the user to feed images in a landscape orientation (which lets them feed faster), while rotating the captured images back to portrait (which is the way the user wants to view them).

Transfer of Multiple ImagesChapter 3, "Application Implementation” discussed the transfer of a single image. Transferring multiple images simply requires looping through the single-image transfer process repeatedly whenever more images are available. Two classes of issues arise when considering multiple image transfer under TWAIN:

• What state transitions are allowable when a session is at an inter-image boundary?

• What facilities are available to support the operation of a document feeder? This includes issues related to high-performance scanning.

This section starts with a review of the single-image transfer process. This is followed by a discussion of options available to an application once the transfer of a single image is complete. Finally, document feeder issues are presented.

To briefly review the single-image transfer process:

• The application enables the Source and the session moves from State 4 to State 5.

• The Source sends the application a MSG_XFERREADY when an image is ready for transfer.

• The application uses DG_IMAGE / DAT_IMAGEINFO / MSG_GET and DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET to get information about the image about to be transferred.

• The application initiates the transfer using a DG_CONTROL / DAT_IMAGExxxxFER / MSG_GET operation. The transfer occurs.

• Following a successful transfer, the Source returns TWRC_XFERDONE.

• The application sends the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation to acknowledge the end of the transfer and learn the number of pending transfers.

If the intent behind transferring a single image is to simply flush it from the Source (for example, an application may want to scan only every other page from a stack placed in a scanner with a document feeder), the following operation suffices:


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• Issue a CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation. As with normal image transfer, this operation tells the Source that the application has completed acquisition of the current image, and the Source responds by reporting the number of pending transfers.

Preparing for Multiple Image Transfer

The DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation issued by the application at the end of every image transfer performs two important functions:

• It returns a count of pending transfers (in TW_PENDINGXFERS.Count)

• It transitions the session to State 6 (Transfer Ready) if the count of pending transfers is nonzero, or to State 5 (Source Enabled) if the count is zero. Recall that the count returned is a positive value if the Source knows the number of images available for acquisition. If the Source does not know the number of images available, the count returned us -1. The latter situation can occur if, for example, a document feeder is in use. Note that not knowing the number of images available includes the possibility that no further images are available; see the description of DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER for more on this.

We have just seen that after the MSG_ENDXFER operation is issued following an image transfer, the session is either in State 6 or State 5; that is, the session is still very much in an active state. If the session is in State 6 (i.e. “an image is available”), the application takes one of two actions so as to eventually transition the session to State 5 (i.e. “Source is ready to acquire an image, though none is available”):

• It continues to perform the single-image transfer process outlined earlier until no more images are available, or

• It issues a DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET to flush all pending transfers from the Source.

Once the session is back in State 5, the application has to decide whether to stay in State 5 or transition down to State 4 (“Source is open, and ready for capability negotiation”.) Two scenarios are possible here.

In one scenario, the application lets the Source control further state transitions. If the Source sends it a MSG_XFERREADY, the application restarts the multiple image transfer loop described above. If the Source sends it a MSG_CLOSEDSREQ (e.g. because the user activated the “Done” trigger on the UI displayed by the Source), the application sends back a DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS, thereby putting the session in State 4.

In the other scenario, the application directly controls session state transitions. For example, the application may want to shut down the current session as soon as the current batch of images have been transferred. In this case, the application issues a DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS as soon as the pending transfers count reaches zero.

It should be noted that there is no “right”, “wrong” or “preferred” scenario for an application to follow when deciding what to do once all images in the current set have been transferred. If an application wants to let the user control the termination of a session explicitly, it may well wait for the Source to send it a MSG_CLOSEDSREQ. On the other hand, the application may have a strong sense of what constitutes a session; for example, it may want to terminate a scan session as soon as a blank page is transferred. In such a case, the application will want to control the condition under which the MSG_DISABLEDS is sent.


Use of a Document Feeder

The term document feeder can refer to a physical device’s automatic document feeder, such as might be available with a scanner, or to the logical feeding ability of an image database. Both input mechanisms apply although the following text uses the physical feeder for its discussion. The topics covered in this section are:

• Controlling whether to scan pages from the document feeder or the platen

• Detecting whether or not paper is ready for scanning

• Controlling scan lookahead

Note that these concepts are applicable to scanners that do not have feeders; see the discussion below for details.

Selecting the Document Feeder

Sometimes the use of a document feeder actually alters how the image is acquired. For instance, a scanner may move its light bar over a piece of paper if the paper is placed on a platen. When a document feeder is used, however, the same scanner might hold the light bar stable and scan the moving paper. To prepare for such variations the application and Source can explicitly agree to use the document feeder. The negotiation for this action must occur during State 4 before the Source is enabled using the following capability.

CAP_FEEDERENABLEDDetermine if a Source has a document feeder available and, if so, select that option.

• To determine if this capability is supported, use a DG_CONTROL / DAT_CAPABILITY / MSG_GET operation. TWRC_FAILURE / TWCC_CAPUNSUPPORTED indicates this Source does not have the ability to select the document feeder.

• If supported, use the DG_CONTROL / DAT_CAPABILITY / MSG_SET operation during State 4.

• Set TW_CAPABILITY.Cap to CAP_FEEDERENABLED.

• Create a container of type TW_ONEVALUE and set it to TRUE. Reference TW_CAPABILITY.hContainer to the container.

• Execute the MSG_SET operation and check the Return Code.

If TWRC_SUCCESS then the feeder is available and your request to use it was accepted. The application can now set other document feeder capabilities.

If TWRC_FAILURE and TWCC_CAPUNSUPPORTED, TWCC_CAPBADOPERATION, or TWCC_BADVALUE then this Source does not have a document feeder capability or does not allow it to be selected explicitly.

Note: If an application wanted to prevent the user from using a feeder, the application should use a MSG_SET operation to set the CAP_FEEDERENABLED capability to FALSE.

Detecting Whether an Image is Ready for Acquisition

Having an image ready for acquisition in the Source device is independent of having a selectable document feeder. There are three possibilities here:


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• The Source cannot tell whether an image is available,

• An image is available for acquisition, or

• No image is available for acquisition

These cases can be detected by first determining whether a Source can tell that image data is available for acquisition (case 1. vs. cases 2. and 3.) and then determining whether image data is available (case 2. vs. case 3.)The capabilities used to do so are as follows:

CAP_PAPERDETECTABLEFirst, determine if the Source can tell that documents are loaded.

• To check if a Source can detect documents, use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.

• Set the TW_CAPABILITY.Cap field to CAP_PAPERDETECTABLE.

• The Source returns TWRC_SUCCESS with the hContainer structure’s value set to TRUE if it can detect a loaded document that is ready for acquisition. If the result code is TWRC_FAILURE with TWCC_CAPUNSUPPORTED or TWCC_BADVALUE, then the Source cannot detect that paper is loaded.

Note: CAP_PAPERDETECTABLE can be used independently of CAP_FEEDERENABLED. Also, an automatic document feeder need not be present for a Source to support this capability; e.g. a scanner that can detect paper on its platen should return TRUE.

The application cannot set this capability. The Source is simply reporting on a condition.

CAP_FEEDERLOADED

Next, determine if there are documents loaded in the feeder.

• To check if pages are present, use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.

• Set the TW_CAPABILITY.Cap field to CAP_FEEDERLOADED.

• The Source returns TRUE if there are documents loaded. The information is in the container structure pointed to by the hContainer field of the TW_CAPABILITY structure.

Note: Neither CAP_FEEDERENABLED nor CAP_PAPERDETECTABLE need be TRUE to use this capability. A FALSE indication from this capability simply indicates that the feeder is not loaded or that the Source’s feeder cannot tell. For a definitive answer, be sure to check CAP_PAPERDETECTABLE.

Controlling Scan Lookahead

With low-end scanners there is usually ample time for the CPU handling the image acquisition to process incoming image data on-the-fly or in the scan delay between pages. However, with higher performance scanners the CPU image processing time for a given page can become a significant fraction of the scan time. This problem can be alleviated if the scanner can scan ahead image data that the CPU has yet to acquire. This data can be buffered in scanner-local memory, or stored in main memory by the Source via a DMA operation while the CPU processes the current image.


Scan look-ahead is not always desirable, however. This is because the decision to continue a scan may be determined by the results of previously scanned images. For example, a scanning application may decide to stop a scan whenever it sees a blank page. If scan look-ahead were always enabled, one or more pages past the blank page may be scanned and transferred to the scanner’s output bin. Such behavior may be incorrect from the point of view of the application’s design

We have argued that the ability to control scan look-ahead is highly desirable. However, a single “enable scan look-ahead” command is insufficient to capture the richness of function provided by some scanners. In particular, TWAIN’s model of document feeding has each image (e.g., sheet of paper) transition through a three stage process.

1. Image is in input bin. This action is taken by the user (for example, by placing a stack of paper into an auto-feeder.)

2. Image is ready for scan. This action causes the next available image to be placed at the start of the scan area. Set the CAP_AUTOFEED capability(described below)to automatically feed images to the start of the scan area.

3. Image is scanned. This action actually causes the image to be scanned. For example, the DG_IMAGE/DAT_IMAGEMEMXFER/MSG_GET operation initiates image transfer to an application via buffered memory. TWAIN allows a Source to pre-fetch images into Source-local memory (even before the application requests them) by setting the CAP_AUTOSCAN capability.

CAP_AUTOFEEDEnable the Source’s automatic document feeding process.

• Use DG_CONTROL / DAT_CAPABILITY / MSG_SET.

• Set the TW_CAPABILITY.Cap field to CAP_AUTOFEED and set the capability to TRUE.

• When set to TRUE, the behavior of the Source is to eject one page and feed the next page after all frames on the first page are acquired. This automatic feeding process will continue whenever there is image data ready for acquisition (and the Source is in an enabled state). CAP_FEEDERLOADED is TRUE showing that pages are in the document feeder.

Note: CAP_FEEDERENABLED must be set to TRUE to use this capability. If not, the Source should return TWRC_FAILURE / TWCC_CAPUNSUPPORTED.

CAP_AUTOSCANEnable the Source’s automatic document scanning process.

• Use DG_CONTROL / DAT_CAPABILITY / MSG_SET.

• Set the TW_CAPABILITY.Cap field to CAP_AUTOSCAN and set the capability to TRUE.

• When set to TRUE, the behavior of the Source is to eject one page and scan the next page after all frames on the first page are acquired. This automatic scanning process will continue whenever there is image data ready for acquisition (and the Source is in an enabled state.

Note: Setting CAP_AUTOSCAN to TRUE implicitly sets CAP_AUTOFEED to TRUE also.


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When your application uses automatic document feeding:

• Set CAP_XFERCOUNT to -1 indicating your application can accept multiple images.

• Expect the Source to return the TW_PENDINGXFERS.Count as -1. It indicates the Source has more images to transfer but it is not sure how many.

• Using automatic document feeding does not change the process of transferring multiple documents described earlier and in Chapter 3, "Application Implementation.”

Control of the Document Feeding by the Application

In addition to automatic document feeding, TWAIN provides an option for an application to manually control the feeding of documents. This is only possible if the Source agrees to negotiate the following capabilities during States 5 and 6 by use of CAP_EXTENDEDCAPS. If CAP_AUTOFEED is set to TRUE, it can impact the way the Source responds to the following capabilities as indicated below.

CAP_FEEDPAGE

• If the application sets this capability to TRUE, the Source will eject the current page (if any) and feed the next page.

• To work as described requires that CAP_FEEDERENABLED and CAP_FEEDERLOADED be TRUE.

• If CAP_AUTOFEED is TRUE, the action is the still the same.

• The page ejected corresponds to the image that the application is acquiring (or is about to acquire). Therefore, if CAP_AUTOSCAN is TRUE and one or more pages have been scanned speculatively, the page ejected may correspond to a page that has already been scanned into Source-local buffers.

CAP_CLEARPAGE

• If the application sets this capability to TRUE, the Source will eject the current page and leave the feeder acquire area empty (that is, with no image ready to acquire).

• To work as described, this requires that CAP_FEEDERENABLED be TRUE and there be a paper in the feeder acquire area to begin with.

• If CAP_AUTOFEED is TRUE, the next page will advance to the acquire area.

• If CAP_AUTOSCAN is TRUE, setting this capability returns TWRC_FAILURE with TWCC_BADVALUE.

CAP_REWINDPAGE

• If the application sets this capability to TRUE, the Source will return the current page to the input area and return the last page from the output area into the acquisition area.

• To work as described requires that CAP_FEEDERENABLED be TRUE.

• If CAP_AUTOFEED is TRUE, the normal automatic feeding will continue after all frames of this page are acquired.

• The page rewound corresponds to the image that the application is acquiring. Therefore, if CAP_AUTOSCAN is TRUE and one or more pages have been scanned speculatively, the page rewound may correspond to a page that has already been scanned into Source-local buffers.


Transfer of Compressed DataWhen using the Buffered Memory mode for transferring images, some Sources may support the transfer of data in a compressed format.

To determine if a Source supports transfer of compressed data and to set the capability

1. Use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation.

2. Set the TW_CAPABILITY.Cap field to ICAP_COMPRESSION.

3. The Source returns information about the compression schemes they support in the container structure pointed to by the hContainer field of TW_CAPABILITY. The identifiers for the compression alternatives all begin with TWCP_, such as TWCP_PACKBITS, and can be seen in the Constants section of Chapter 8, "Data Types and Data Structures” and in the TWAIN.H file.

4. If you wish to negotiate for the transfer to use one of the compression schemes shown, use the DG_CONTROL / DAT_CAPABILITY / MSG_SET operation.

The TW_IMAGEMEMXFER structure is used with the DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation. The structure looks like this:

typedef struct {

TW_UINT16 Compression; /* A TWCP_xxxx constant */ TW_UINT32 BytesPerRow; TW_UINT32 Columns; TW_UINT32 Rows; TW_UINT32 XOffset; TW_UINT32 YOffset; TW_UINT32 BytesWritten; TW_MEMORY Memory;} TW_IMAGEMEMXFER, FAR *pTW_IMAGEMEMXFER;

When compressed strips of data are transferred:

• The BytesPerRow field will be set to 0. The Columns, Rows, XOffset, and YOffset fields will contain TWON_DONTCARE32 indicating the fields hold invalid values. (The original image height and width are available by using the DG_IMAGE / DAT_IMAGEINFO / MSG_GET operation during State 6 prior to the transfer.)

• Transfer buffers are always completely filled by the Source. For compressed data, it is very likely that at least one partial line will be written into the buffer.

• The application is responsible for deallocating the buffers.

When compressed, tiled data are transferred:

• All fields in the structure contain valid data. BytesPerRow, Columns, Rows, XOffset, and YOffset all describe the uncompressed tile. Compression and BytesWritten describe the compressed tile.


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• In this case, unlike with compressed, strip data transfer, the Source allocates the transfer buffers. This allows the Source to create buffers of differing sizes so that complete, compressed tiles can be transferred to the application intact (not split between sequential buffers). Under these conditions, the application should set the fields of the TW_MEMORY structure so Flags is TWMF_DSOWNS, Length is TWON_DONTCARE32 and TheMem is NULL. The Source must assume that the application will keep the previous buffer rather than releasing it. Therefore, the Source must allocate a new buffer for each transfer.

• The application is responsible for deallocating the buffers.

• Finally, the application cannot assume that the tiles will be transferred in any particular, logical order.

JPEG Compression

TWAIN supports transfer of several forms of compressed data. JPEG compression is one of them. The JPEG compression algorithm provides compression ratios in the range of 10:1 to 25:1 for grayscale and full-color images, often without causing visible loss of image quality. This compression, which is created by the application of a series of “perceptual” filters, is achieved in three stages:

Color Space Transformation and Component Subsampling (Color Images Only, Not for Grayscale)

The human eye is far more sensitive to light intensity (luminance) than it is to light frequency (chrominance, or “color”) since it has, on average, 100 million detectors for brightness (the “rods”) but only about 6 million detectors for color (the “cones”). Substantial image compression can be achieved simply by converting a color image into a more efficient luminance/chrominance color space and then subsampling the chrominance components.

This conversion is provided for by the TW_JPEGCOMPRESSION structure. By specifying the TW_JPEGCOMPRESSION.ColorSpace = TWPT_YUV, Source RGB data is converted into more space-efficient YUV data (better known as CCIR 601-1 or YCbCr). TW_JPEGCOMPRESSION.SubSampling specifies the ratio of luminance to chrominance samples in the resulting YUV data stream, and a typical choice calls for two luminance samples for every chrominance sample. This type of subsampling is specified by entering 0x21102110 into the TW_JPEGCOMPRESSION.SubSampling field. A larger ratio of four luminance samples for every chrominance sample is represented by 0x41104110. To sample two luminance values for every chrominance sample in both the horizontal and vertical axes, use a value of 0x21102110.

Application of the Discrete Cosine Transform (DCT) and Quantization

The original components (with or without color space conversion) are next mathematically converted into a spatial frequency representation using the DCT and then filtered with quantization matrices (each frequency component is divided by its corresponding member in a quantization matrix). The quantization matrices are specified by TW_JPEGCOMPRESSION.QuantTable[] and up to four quantization matrices may be defined for up to four different original components. TW_JPEGCOMPRESSION.QuantMap[] maps the particular original component to its respective quantization matrix.

Note: Defaults are provided for the quantization map and tables are suggested in Section K of the JPEG Draft International Standard, version 10918-1 are used as the default tables for QuantTable, HuffmanDC, and HuffmanAC by TWAIN. The default tables are selected by putting NULL into each of the TW_JPEGCOMPRESSION.QuantTable[] entries.


Huffman encoding

The resulting coefficients from the DCT and quantization steps are further compressed in one final stage using a loss-less compression algorithm called Huffman encoding. Application developers can provide Huffman tables, though typically the default tables—selected by writing NULL into TW_JPEGCOMPRESSION.HuffmanDC[] and TW_JPEGCOMPRESSION.HuffmanAC[]—yield very good results.

The algorithm optionally supports the use of restart marker codes. The purpose of these markers is to allow random access to strips of compressed data in JPEG data stream. They are more fully described in the JPEG specification.


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See Chapter 8, "Data Types and Data Structures” for the definition of the TW_JPEGCOMPRESSION data structure. Example data structures are shown below for RGB image compression and grayscale image compression:

/* RGB image compression - YUV conversion and 2:1:1 chrominance *//* subsampling */typedef struct TW_JPEGCOMPRESSION myJPEG;myJPEG.ColorSpace = TWPT_YUV; // convert RGB to YUVmyJPEG.SubSampling = 0x21102110; // 2 Y for each U, VmyJPEG.NumComponents = 3; // Y, U, VmyJPEG.RestartFrequency = 0; // No restart markersmyJPEG.QuantMap[0] = 0; // Y component uses table0myJPEG.QuantMap[1] = 1; // U component uses table 1myJPEG.QuantMap[2] = 1; // V component uses table 1myJPEG.QuantTable[0] = NULL; // select defaults for quant // tablesmyJPEG.QuantTable[1] = NULL; //myJPEG.QuantTable[2] = NULL; //myJPEG.HuffmanMap[0] = 0; // Y component uses DC & AC // table 0myJPEG.HuffmanMap[1] = 1; // U component uses DC & AC // table 1myJPEG.HuffmanMap[2] = 1; // V component uses DC & AC // table 1myJPEG.HuffmanDC[0] = NULL; // select default for Huffman // tablesmyJPEG.HuffmanDC[1] = NULL; //myJPEG.HuffmanAC[0] = NULL; //myJPEG.HuffmanAC[1] = NULL; ///* Grayscale image compression - no color space conversion or *//* subsampling */typedef struct TW_JPEGCOMPRESSION myJPEG;myJPEG.ColorSpace = TWPT_GRAY; // Grayscale datamyJPEG.SubSampling = 0x10001000; // no chrominance componentsmyJPEG.NumComponents = 1; // GrayscalemyJPEG.RestartFrequency = 0; // No restart markersmyJPEG.QuantMap[0] = 0; // select default for quant // mapmyJPEG.QuantTable[0] = NULL; //myJPEG.HuffmanMap[0] = 0; // select default for Huffman // tablesmyJPEG.HuffmanDC[0] = NULL; //myJPEG.HuffmanAC[0] = NULL; //

The resulting compressed images from these examples will be compatible with the JPEG File Interchange Format (JFIF version 1.1) and will therefore be usable by a variety of applications that are JFIF-aware.


Alternative User InterfacesAlternatives to Using the Source Manager’s Select Source Dialog

TWAIN ships its Source Manager code to act as the communication vehicle between application and Source. One of the services the Source Manager provides is locating all available Sources that meet the application’s requirements and presenting those to the user for selection.

It is recommended that the application use this approach. However, the application is not required to use this service. Two alternatives exist:

• The application can develop and present its own custom selection interface to the user. This is presented in response to the user choosing Select Source... from its menu.

• Or, if the application is dedicated to control of a specific Source, the application can transparently select the Source. In this case, the application does not functionally need to have a Select Source... option in the menu but a grayed-out one should be displayed for consistency with all other TWAIN-compliant applications.

Displaying a custom selection interface:

1. Use the DG_CONTROL / DAT_IDENTITY / MSG_GETFIRST operation to have the Source Manager locate the first Source available. The name of the Source is contained in the TW_IDENTITY.ProductName field. Save the TW_IDENTITY structure.

2. Use the DG_CONTROL / DAT_IDENTITY / MSG_GETNEXT to have the Source Manager locate the next Source. Repeatedly use this operation until it returns TWRC_ENDOFLIST indicating no more Sources are available. Save the TW_IDENTITY structure.

3. Use the ProductName information to display the choices to the user. Once they have made their selection, use the saved TW_IDENTITY structure and the DG_CONTROL / DAT_IDENTITY / MSG_OPENDS operation to have the Source Manager open the desired Source. (Note, using this approach, as opposed to the MSG_USERSELECT operation, the Source Manager does not update the system default Source information to reflect your choice.)

Transparently selecting a Source:

If the application wants to open the system default Source , use the DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULT operation to have the Source Manager locate the default Source and fill the TW_IDENTITY structure with information about it. The name of the Source is contained in the TW_IDENTITY.ProductName field. Save the TW_IDENTITY structure.ORIf you know the ProductName of the Source you wish to use and it is not the system default Source, use the DG_CONTROL / DAT_IDENTITY / MSG_GETFIRST and DG_CONTROL / DAT_IDENTITY / MSG_GETNEXT operations to have the Source Manager locate each Source. You must continue looking at Sources until you verify that the desired Source is available. Save the TW_IDENTITY structure when you locate the Source you want. If the Return Code TWRC_ENDOFLIST appears before the desired Source is located, it is not available.


Chapter 4

Use the saved TW_IDENTITY structure and the DG_CONTROL / DAT_IDENTITY / MSG_OPENDS operation to have the Source Manager open the desired Source. (Note, using this approach, rather than MSG_USERSELECT, the Source Manager does not update the system default Source information to reflect your choice.)

Alternatives to Using the Source’s User Interface

Just as with the Source Manager’s Select Source dialog, the application may ask to not use the Source’s user interface. Certain types of applications may not want to have the Source’s user interface displayed. An example of this can be seen in some text recognition packages that wish to negotiate a few capabilities (i.e. pixel type, resolution, page size) and then proceed directly to acquiring and transferring the data.

To Enable the Source without Displaying its User Interface

• Use the DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS operation.

• Set the ShowUI field of the TW_USERINTERFACE structure to FALSE.

• When the command is received and accepted (TWRC_SUCCESS), the Source does not display a user interface but is armed to begin capturing data. For example, in a flatbed scanner, the light bar will light and begin to move. A handheld scanner will be armed and ready to acquire data when the “go” button is pressed on the scanner. Other devices may respond differently but they all will either begin acquisition immediately or be armed to begin acquiring data as soon as the user interacts with the device.

Capability Negotiation is Essential when the Source’s User Interface is not Displayed

• Since the Source’s user interface is not displayed, the Source will not be giving the user the opportunity to select the information to be acquired, etc. Unless default values are acceptable, current values for all image acquisition and control parameters must be negotiated before the Source is enabled, i.e. while the session is in State 4.

When TW_USERINTERFACE.ShowUI is set to FALSE:

• The application is still required to pass all events to the Source (via the DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT operation) while the Source is enabled.

• The Source must display the minimum possible user interface containing only those controls required to make the device useful in context. In general, this means that no user interface is displayed, however certain devices may still require a trigger to initiate the scan.

• The Source still displays a progress indicator during the acquisition. The application can suppress this by setting CAP_INDICATORS to FALSE, if the Source specified CAP_UICONTROLLABLE as TRUE.

• The Source still displays errors and other messages related to the operation of its device. The application can suppress this by setting CAP_INDICATORS to FALSE, if the Source specified CAP_UICONTROLLABLE as TRUE..

• The Source still sends the application a MSG_XFERREADY notice when the data is ready to be transferred.

• The Source may or may not send a MSG_CLOSEDSREQ to the application asking to be closed since this is often user-initiated. Therefore, after the Source has returned to State 5 (following the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation and the


TW_PENDINGXFERS.Count = 0), the application can send the DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS operation.

Note: Some Sources may display the UI even when ShowUI is set to FALSE. An application can determine whether ShowUI can be set by interrogating the CAP_UICONTROLLABLE capability. If CAP_UICONTROLLABLE returns FALSE but the ShowUI input value is set to FALSE in an activation of DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS, the enable DS operation returns TWRC_CHECKSTATUS but displays the UI regardless. Therefore, an application that requires that the UI be disabled should interrogate CAP_UICONTROLLABLE before issuing MSG_ENABLEDS.

Modal Versus Modeless User Interfaces

The Source Manager’s user interface is a modal interface but the Source may provide a modeless or modal interface. Here are the differences:

Modeless

When a Source uses a modeless user interface, although the Source’s interface is displayed, the user is still able to access the application by clicking on the application’s window and making it active.The user is expected to click on a Close button on the Source’s user interface when they are ready for that display to go away. The application must NOT automatically close a modeless Source after the first (or any subsequent) transfer, even if the application is only interested in receiving a single transfer. If the application closes the Source before the user requests it, the user is likely to become confused about why the window disappeared. Wait until the user indicates the desire to close the Source’s window and the Source sends this request (MSG_CLOSEDSREQ) to the application before closing the Source.

Modal

A Source using a modal user interface prevents the user from accessing other windows. For Windows only, if the interface is application modal, the user cannot access other applications but can still access system utilities. If the interface is system modal (which is rare), the user cannot access anything else at an application or system level. A system modal dialog might be used to display a serious error message, like a UAE.If using a modal interface, the Source can perform only one acquire during a session although there may be multiple frames per acquisition. The Source will send a close request to the application following the completion of the data transfer. Again, the application waits to receive this request.

The Source indicates if it is using a modeless or modal interface after the application enables it using the DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS operation. The data structure used in the operation (TW_USERINTERFACE) contains a field, ShowUI, which is set by the application to indicate whether the Source should display its user interface. If the application requests the user interface be shown, it may also set the ModalUI field to indicate if it wishes the Source’s GUI to run modal (TRUE) or modeless (FALSE).

When requested by the Source, the application uses the DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS operation to remove the Source’s user interface.


Chapter 4

Grayscale and Color Information for an ImageThere are operation triplets in TWAIN that allow the application developer to interact with and influence the grayscale or color aspect of the images that a Source transfers to the application. The following operations provide these abilities:

• CIE Color DescriptorsDG_IMAGE / DAT_CIECOLOR / MSG_GET

• Grayscale ChangesDG_IMAGE / DAT_GRAYRESPONSE / MSG_RESET

DG_IMAGE / DAT_GRAYRESPONSE / MSG_SET

• Palette Color DataDG_IMAGE / DAT_PALETTE8 / MSG_GET

DG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULTDG_IMAGE / DAT_PALETTE8 / MSG_RESETDG_IMAGE / DAT_PALETTE8 / MSG_SET

• RGB Response Curve DataDG_IMAGE / DAT_RGBRESPONSE / MSG_RESET

DG_IMAGE / DAT_RGBRESPONSE / MSG_RESET

CIE Color Descriptors

The CIE XYZ approach is a method for storing color data which simplifies doing mathematical manipulations on the data. (The topic of CIE XYZ color space is discussed thoroughly in Appendix A.)

If your application wishes to receive the image data in this format:

1. You must ensure that the Source is able to provide data in CIE XYZ format. To check this, use the DG_CONTROL / DAT_CAPABILITY / MSG_GET operation and get information on the ICAP_PIXELTYPE. If TWPT_CIEXYZ is returned as one of the supported types, the Source can provide data in CIE XYZ format.

2. After verifying that the Source supports it, the application can specify that data transfers should use the CIE XYZ format by invoking a DG_CONTROL / DAT_CAPABILITY / MSG_SET operation on the ICAP_PIXELTYPE. Use a TW_ONEVALUE container whose value is TWPT_CIEXYZ.

To determine the parameters that were used by the Source in converting the color data into the CIE XYZ format, use the DG_IMAGE / DAT_CIECOLOR / MSG_GET operation following the transfer of the image.

Grayscale Changes

(The grayscale operations assume that the application has instructed the Source to provide grayscale data by setting its ICAP_PIXELTYPE to TWPT_GRAY and the Source is capable of this.)


The application can request that the Source apply a transfer curve to its grayscale data prior to transferring the data to the application. To do this, the application uses the DG_IMAGE / DAT_GRAYRESPONSE / MSG_SET operation. The desired transfer curve information is placed by the application within the TW_GRAYRESPONSE structure (the actual array is of type TW_ELEMENT8). The application must be certain to check the Return Code following this request. If the Return Code is TWRC_FAILURE and the Condition Code shows TWCC_BADPROTOCOL, this indicates the Source does not support grayscale response curves (despite supporting grayscale data).

If the Source allows the application to set the grayscale transfer curve, there must be a way to reset the curve to its original non-altered value. Therefore, the Source must have an “identity response curve” which does not alter grayscale data but transfers it exactly as acquired. When the application sends the DG_IMAGE / DAT_GRAYRESPONSE / MSG_RESET operation, the Source resets the grayscale response curve to its identity response curve.

Palette Color Data

(The palette8 operations assume that the application has instructed the Source to use the TWPT_PALETTE type for its ICAP_PIXELTYPE and that the Source has accepted this.)

The DAT_PALETTE8 operations allow the application to inquire about a Source’s support for palette color data and to set up a palette color transfer. The operations are specialized for 8-bit data, whether grayscale or color (8-bit or 24-bit). The MSG_GET operation allows the application to learn what palette was used by the Source during the image acquisition. The application should always execute this operation immediately after an image transfer rather than before because the Source may optimize the palette during the acquisition process. Some Sources may allow an application to define the palette to be used during image acquisition via the MSG_SET operation. Be sure to check the Return Code to verify that it is TWRC_SUCCESS following a MSG_SET operation. That is the only way to be certain that your requested palette will actually be used during subsequent palette transfers.

RGB Response Curve Data

(The RGB Response curve operations assume that the application has instructed the Source to provide RGB data by setting its ICAP_PIXELTYPE to TWPT_RGB and the Source is capable of this.)

The application can request that the Source apply a transfer curve to its RGB data prior to transferring the data to the application. To do this, the application uses the DG_IMAGE / DAT_RGBRESPONSE / MSG_SET operation. The desired transfer curve information is placed by the application within the TW_RGBRESPONSE structure (the actual array is of type TW_ELEMENT8). The application must be certain to check the Return Code following this request. If the Return Code is TWRC_FAILURE and the Condition Code shows TWCC_BADPROTOCOL, this indicates the Source does not support RGB response curves (despite supporting RGB data).

If the Source allows the application to set the RGB response curve, there must be a way to reset the curve to its original non-altered value. Therefore, the Source must have an “identity response curve” which does not alter RGB data but transfers it exactly as acquired. When the application sends the DG_IMAGE / DAT_RGBRESPONSE / MSG_RESET operation, the Source resets the RGB response curve to its identity response curve.


Chapter 4

Contrast, Brightness, and Shadow ValuesThere is considerable confusion about what is the appropriate way to present these actual features for a particular device. Anyone who has attempted to support these capabilities knows that the recommended ranges do not accurately reflect the capabilities of real world devices. Data source developers have tried many different methods of getting the correct response for their data source, and not all are consistent.

By providing a meaningful step size, or by providing a different container, a data source can provide the application with enough information to accurately model the actual ability of the device. For an application that wishes to present a custom User Interface for this type of capability, it is not really useful to the user if it provides 2000 steps from -1000 to +1000, especially if the device really only supports a small number of levels.

Since both data source developers and application developers read the same specification, it can be assumed that it is not acceptable to provide values that do not fit within the documented ranges for these types of capabilities.

The following suggestion is an example of how to follow the specification, and provide the most accurate values for the particular data source.

Example 1: ICAP_BRIGHTNESS Supporting Only Three Levels

The specification requirement stated in Chapter 10, "Capabilities” is as follows:

“Source should normalize the values into the range. Make sure that a ‘0' value is available as the Current Value when the Source starts up. If the Source’s ± range is asymmetric about the ‘0’ value, set range maxima to ±1000 and scale homogeneously from the ‘0’ value in each direction. This will yield a positive range whose step size differs from the negative range’s step size.”

Note: It should be expanded in this statement that for a step size that differs in the negative and positive range, a TW_ENUMERATION container must be used. A TW_RANGE container is not suitable for representing a non-linear step size).

Assume the actual device simply supports the options normal, lighten, and darken. These can fit into the constraints by mapping actual values to required values:

Normal = 0

Lighten = -1000

Darken = 1000

These values can be placed in a TW_RANGE container with a step size of 1000, or into a TW_ENUMERATION containing only the 3 values. { -1000, 0, 1000 }, the current and default values are 0.


5Source Implementation

Chapter ContentsThe Structure of a Source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-2Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-3Sources and the Event Loop. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-4User Interface Guidelines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-7Capability Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-10Data Transfers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-12Error Handling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-15Memory Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-17Requirements for a Source to be TWAIN-Compliant . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-18Other Topics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-22

Companies that produce image-acquisition devices, and wish to gain the benefits of being TWAIN-compliant, must develop TWAIN-compliant Source software to drive their device. The Source software is the interface between TWAIN’s Source Manager and the company’s physical (or logical) device. To write effective Source software, the developer must be familiar with the application’s expectations as discussed in the other chapters of this document.

Mac OS X includes two high-level native development environments that you can use for your application’s graphical user interface: Carbon, and Cocoa. These environments are full-featured development environments in their own right, and you can write TWAIN applications and TWAIN Data Sources in any one of these environments.

Because both Carbon and Cocoa change the event handling mechanism (no WaitNextEvent loops), these paragraphs update and extend the section of the previous specification that describes how to modify the application event loop to support TWAIN.

Carbon and Cocoa-based Mac OS X TWAIN applications are required to supply an event handler callback function that the TWAIN DSM will call. Carbon applications using the Classic Event Manager (WaitNextEvent) should continue to route all events through the Data Source. However, Data Sources on Mac OS X can no longer use the Classic Event Manager.


Chapter 5

The Structure of a SourceThe following sections describe the structure of a source.

On Windows

Implementation

The Source is implemented as a Dynamic Link Library (DLL). Sources should link to TWAIN.LIB at link time. The Source will not run stand-alone. The DLL typically runs within the (first) calling application’s heap although DLLs may be able to allocate their own heap and stack space. There is only one copy of the DLL’s code and data loaded at run-time, even if more than one application accesses the Source. For more information regarding DLLs on Win32s, Windows95, and Windows NT please refer to Microsoft documents.

Naming and Location

The DLL’s file name must end with a .DS extension. The Source Manager recursively searches for your Source in the TWAIN sub-directory of the Windows directory (typically C:\WINDOWS on Windows 95/98, or C:\WINNT on Windows NT). To reduce the chance for naming collisions, each Source should create a sub-directory beneath TWAIN, giving it a name relevant to their product. The Source DLLs are placed there. Supporting files may be placed there as well, but since this is a system directory which may only be modifiable by the System Administrator, Sources must not write any information into this directory after the installation.

Entry Points and Segment Attributes

• Every Source is required to have a single entry point called DS_Entry (see Chapter 6, "Entry Points and Triplet Components”). For 16-bit sources only, in order to speed up the Source Manager’s ability to identify Sources, the Source entry point DS_Entry( ) and the code to respond to the DG_CONTROL / DAT_IDENTITY / MSG_GET operation must reside in a segment marked as PRELOAD. All other segments should be marked as LOADONCALL (with the exception of any interrupt handler that may exist in the Source which needs to be in a FIXED code segment).

Resources

• Version Information - The Microsoft VER.DLL is included with the TWAIN toolkit for use by your installation program, if you have one, to validate the version of the currently installed Source Manager. Sources should be marked with the Version information capability defined in Microsoft Windows 3.1. To do this, you can use the resource compiler from the version 3.1 SDK. VER.DLL and the version stamping are also compatible with Microsoft Windows version 3.0.

• Icon Id - Future versions of the TWAIN Source Manager may display the list of available Sources using a combination of the ProductName (in the Source’s TW_IDENTITY structure) and an Icon (as the Macintosh version currently does). Therefore, it is recommended that you add this icon into your Source resource file today. This will allow your Source to be immediately compatible with any upcoming changes. The icon should be identified using TWON_ICONID from the TWAIN.H file.


General Notes

• GlobalNotify - Microsoft Windows allows only one GlobalNotify handler per task. As the Source resides in the application heap, the Source should not use the GMEM_NOTIFY flag on the memory blocks allocated as this may disrupt the correct behavior of the application that uses GlobalNotify.

• Windows Exit Procedure (WEP) - During the WEP, the Source is being unloaded by Microsoft Windows. The Source should make sure all the resources it allocated and owns get released whether or not the Source was terminated properly.

On Macintosh

Implementation

A Source on a Macintosh is implemented as a bundle. The Source will not run standalone. A separate copy of the Source’s code will be made for each application that opens the Source.

Naming and Location

The extension for a Source is ds. The Source Manager will search for bundles with this extension in the /Library/Image Capture/TWAIN Data Sources/ folder. It is recommended that each Source bundle contains any other files it may require.

Compatibility with Older Data Sources

Pre Mac OS X Data Source are not compatible with the TWAIN implementation on Mac OS X.

Operation Triplets In Chapter 3, "Application Implementation,” we introduced all of the triplets that an application can send to the Source Manager or ultimately to a Source. There are several other triplet operations which do not originate from the application. Instead, they originate from the Source Manager or Source and are introduced in this chapter. All defined operation triplets are listed in detail inChapter 7, "Operation Triplets.”

Triplets from the Source Manager to the Source

There are three operation triplets that are originated by the Source Manager. They are:

DG_CONTROL / DAT_IDENTITY

MSG_GET Returns the Source’s identity structure

MSG_OPENDS Opens and initializes the Source

MSG_CLOSEDS Closes and unloads the Source

The DG_CONTROL / DAT_IDENTITY / MSG_GET operation is used by the Source Manager to identify available Sources. It may send this operation to the Source at any time and the Source must be prepared to respond informatively to it. That means, the Source must be able to return its identity structure before being opened by the Source Manager (with the MSG_OPENDS command). The Source’s initially loaded code segment must be able to perform this function


Chapter 5

without loading any additional code segments. This allows quick identification of all available Sources and is the only operation a Source must support before it is formally opened.

The TW_IDENTITY structure looks like this:

typedef struct {

TW_UINT32 Id;

TW_VERSION Version;

TW_UINT16 ProtocolMajor;

TW_UINT16 ProtocolMinor;

TW_UINT32 SupportedGroups;

TW_STR32 Manufacturer;

TW_STR32 ProductFamily;

TW_STR32 ProductName;

} TW_IDENTITY, FAR *pTW_IDENTITY;

The ProductName field in the Source’s TW_IDENTITY structure should uniquely identify the Source. This string will be placed in the Source Manager’s Select Source... dialog for the user. (The file name of the Source should also approximate the ProductName, if possible, to add clarity for the user at installation time.) Fill in all fields except the Id field which will be assigned by the Source Manager. The unique Id number that identifies your Source during its current session will be passed to your Source when it is opened by the MSG_OPENDS operation. Sources on Windows must save this TW_IDENTITY.Id information for use when sending notifications from the Source to the application.

Sources and the Event Loop

Handling Events

On Windows, when a Source is enabled (i.e. States 5, 6, and 7), the application must pass all events (messages) to the Source. Since the Source runs subservient to the application, this ensures that the Source will receive all events for its window. The event will be passed in the TW_EVENT data structure that is referenced by a DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT command.

On Mac OS X, the Data source either uses Carbon or Cocoa. A Carbon based Data Source has to install Carbon Event Handler for all UI elements. A Cocoa Data Source gets the UI event handling for free.

Note: Starting with TWAIN 1.8, it is now possible for events to be managed in State 4 only to support CAP_DEVICEEVENTS. This is a fundamental change from previous TWAIN behavior that has been added to allow the Source to notify the Application of important changes in the state of the Source even while in State 4. Note also that the default value for CAP_DEVICEEVENTS (if supported) must be an empty TW_ARRAY, indicating the


event reporting is turned off. This is essential to allow backward compatibility with pre-1.8 Applications.

Routing all messages to all connected Sources while they are enabled places a burden on the application and creates a potential performance bottleneck. Therefore, the Source must process the incoming events as quickly as possible. The Source should examine each incoming operation before doing anything else. Only one operation’s message field says MSG_PROCESSEVENT so always look at the message field first. If it indicates MSG_PROCESSEVENT then:

Immediately determine if the event belongs to the Source.

If it doesSet the Return Code for the operation to TWRC_DSEVENTSet the TWMessage field to MSG_NULLProcess the event

ElseSet the Return Code to TWRC_NOTDSEVENT Set the TWMessage field to MSG_NULLReturn to the application immediately

If the Source developer fails to process events with this high priority, the user may see degraded performance whenever the Source is frontmost which reflects poorly on the Source.

On Windows, the code fragment looks like the following:

TW_UINT16 CALLBACK DS_Entry(pTW_IDENTITY pSrc,

TW_UINT32 DG,

TW_UINT16 DAT,

TW_UINT16 MSG,

TW_MEMREF pData)

{

TWMSG twMsg;

TW_UINT16 twRc;

//Valid states 5 – 7 (or 4 – 7 if CAP_DEVICEEVENTS has been

// negotiated to anything other than its default value of an empty

// TW_ARRAY). As soon as the application has enabled the

// Source it must being sending the Source events. This allows the

// Source to receive events to update its user interface and to

// return messages to the application. The app sends down ALL

// message, the Source decides which ones apply to it.

if (MSG == MSG_PROCESSEVENT)


Chapter 5

{

if (hImageDlg && IsDialogMessage(hImageDlg, (LPMSG)(((pTW_EVENT)pData)->pEvent)))

{

twRc = TWRC_DSEVENT;

// The source should, for proper form, return a MSG_NULL for

// all Windows messages processed by the Data Source

((pTW_EVENT)pData)->TWMessage = MSG_NULL;

}

else

{

// notify the application that the source did not

// consume this message

twRc = TWRC_NOTDSEVENT;

((pTW_EVENT)pData)->TWMessage = MSG_NULL;

}

}

else

{

// This is a Twain message, process accordingly.

// The remainder of the Source’s code follows...

}

return twRc;

}

The Windows IsDialogMessage( ) call is used in this example. Sources can also use other Windows calls such as TranslateAccelerator( ) and TranslateMDISYSAccel( ).

Communicating to the Application

As explained in Chapter 3, "Application Implementation”, there are four instances where the Source must originate and transmit a notice to the application:

• When it has data ready to transfer (MSG_XFERREADY)

• The Source must send this message when the user clicks the “GO” button on the Source’s user interface or when the application sends a DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS operation with ShowUI = FALSE. The Source will transition from State 5 to State 6. The application should now perform their inquiries regarding TW_IMAGEINFO and capabilities. Then, the application issues a DG_IMAGE / DAT_IMAGExxxxXFER / MSG_GET


operation to begin the transfer process. Typically, though it is not required, it is at this time that a flatbed scanner (for example) will begin simultaneously to acquire and transfer the data using the specified transfer mode.

When it needs to have its user interface disabled (MSG_CLOSEDSREQ)

• Typically, the Source will send this only when the user clicks on the CLOSE button on the Source’s user interface or when an error occurs which is serious enough to require terminating the session with the application. The Source should be in (or transition to) State 5. The application should respond by sending a DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS operation to transition the session back to State 4.

• When the user has pressed the OK button in a Source’s dialog that was brought up with DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDSUIONLY (MSG_CLOSEDSOK).

• Applications should use this event as the indicator that the user has set all the desired attributes from the Source’s GUI.

• When the Source needs to report a Device Event. Note that the application must explicitly request the Source to supply Device Events (MSG_DEVICEEVENT). Sources must only provide those Device Events requested by a Source through the CAP_DEVICEEVENT capability. The default for this capability when the Source starts up is an empty TW_ARRAY, indicating that no Device Events are being reported. Applications that turn on Device Events must issue a DG_CONTROL / DAT_DEVICEEVENT / MSG_GET command as soon as possible after receiving a Device Event.

These notices are sent differently on Windows versus Macintosh systems.

On Windows

The Source creates a call to DSM_Entry (the entry point in the Source Manager) and fills the destination with the TW_IDENTITY structure of the application. The Source uses one of the following triplets:

DG_CONTROL / DAT_NULL / MSG_XFERREADY

DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQ

The Source Manager, on Windows, recognizes the notice and makes sure the message is received correctly by the application.

On MacintoshPlease refer to the callback mechanism described in Chapter 3, "Application Implementation.”

User Interface GuidelinesEach TWAIN-compliant Source provides a user interface to assist the user in acquiring data from their device. Although each device has its own unique needs, the following guidelines are provided to increase consistency among TWAIN-compliant devices.


Chapter 5

Displaying the User Interface

The application issues DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS to transition the session from State 4 to 5.

The TW_USERINTERFACE data structure contains these fields:

• ShowUI - If set to TRUE, the Source displays its user interface.If FALSE, the application will be providing its own.

• hParent - Used by Sources on Windows only. It indicates the application’s window handle. This is to be designated as the Source’s parent for the dialog so it is a proper child of its parent application.

• ModalUI - To be set by the Application to TRUE or FALSE.

Sources are not required to allow themselves to be enabled without showing their user interface (ShowUI = FALSE) but it is strongly recommended that they allow this. If your Source cannot be used without its user interface, it should enable showing the user interface (just as if ShowUI = TRUE) and return TWRC_CHECKSTATUS. All Sources, however, must report whether or not they honor ShowUI set to FALSE via the CAP_UICONTROLLABLE capability. This allows applications to know whether the Source-supplied user interface can be suppressed before it is displayed.

When the user interface is disabled (by DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS), a pointer to a TW_USERINTERFACE is included in the pData parameter.

Modal versus Modeless Interfaces

As stated in Chapter 4, "Advanced Application Implementation”, the Source’s user interface may be modal or modeless. The modeless approach gives the user more control and is recommended whenever practical. Refer to the information following this table for specifics about Windows and Macintosh implementation.

Error and Device Control Indicators

The Source knows what is happening with the device it controls. Therefore, the Source is responsible for determining when and what information regarding errors and device controls (ex. "place paper in document feeder") should be presented to the user. Error information should be placed by the Source on top of either the application's or Source's user interface. Do not present error messages regarding capability negotiation to the user since this should be transparent.

Progress Indicators

The Source should display appropriate progress indicators for the user regarding the acquisition and/or transfer processes. The Source must provide this information regardless of whether or not its user interface is displayed (ShowUI equals TRUE or FALSE). To suppress the indicators when the user interface is not displayed, the application should negotiate the CAP_INDICATORS capability to be FALSE.


Impact of Capability Negotiation

If the Source has agreed to limit the Available Values and/or to set the Current Value, the interface should reflect the negotiation. However, if a capability has not been negotiated by the application, the interface should not be modified (don’t gray out a control because it wasn’t negotiated.)

Advanced Topics

If a Source can acquire from more than one device, the Source should allow the user to choose which device they wish to acquire from. Provide the user with a selection dialog that is similar to the one presented by the Source Manager’s Select Source... dialog.

Implementing Modal and Modeless User Interfaces

On Windows

You cannot use the modal dialog creation call DialogBox( ) to create the Source’s user interface main window. To allow event processing by both the application and the Source, this call cannot be used. Modal user interfaces in Source are not inherently bad, however. If a modal user interface makes sense for your Source, use either the CreateDialog( ) or CreateWindow( ) call.

Modal (App Modal)

It is recommended that the Source’s main user interface window be created with a modeless mechanism. Source writers can still decide to make their user interface behave modally if they choose. It is even appropriate for a very simple “click and go” interface to be implemented this way.

This is done by first specifying the application’s window handle (hWndParent) as the parent window when creating the Source’s dialog/window and second by enabling/disabling the parent window during the MSG_ENABLEDS / MSG_DISABLEDS operations. Use EnableWindow(hWndParent, FALSE) to disable the application window and EnableWindow(hWndParent, TRUE) to re-enable it.

Modeless

If implementing a modeless user interface, specify NULL as the parent window handle when creating the Source’s dialog/window. Also, it is suggested that you call BringWindowToTop( ) whenever a second request is made by the same application or another application requesting access to a Source that supports multiple application connections.

On Macintosh

It is recommended that the Source’s main user interface window be created with a modeless mechanism. Source writers can still decide to make their user interface behave modally if they choose. It is even appropriate for a very simple “click and go” interface to be implemented this way.


Chapter 5

Capability NegotiationCapability negotiation is a critical area for a Source because it allows the application to understand and influence the images that it receives from your Source.

Inquiries From the Application

While the Source is open but not yet enabled (from DG_CONTROL / DAT_IDENTITY / MSG_OPENDS until DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS), the application can inquire the values of all supported capabilities, and request to set those values.

Once the Source is enabled, the application may only inquire about capabilities. An attempt to set a capability should fail with TWRC_FAILURE and TWCC_SEQERROR (unless CAP_EXTENDEDCAPS was negotiated).

Responding to Inquiries

Sources must be able to respond to capability inquiries with current values at any time the Source is open (i.e. from MSG_OPENDS until MSG_CLOSEDS or before posting a MSG_CLOSEDSREQ).

A Source should respond with information to any capability that applies to your device. Only if a capability has no match with your device’s features should you respond with TWRC_FAILURE / TWCC_BADCAP.

Refer toChapter 10, "Capabilities” for the complete list of TWAIN-defined capabilities.

Responding to Requests to Set Capabilities

If the requested value is invalid or the Source does not support the capability, then return TWRC_FAILURE / TWCC_CAPUNSUPPORTED. If the requested operation (MSG_SET, MSG_RESET, etc.) is not supported, then return TWRC_FAILURE / TWCC_CAPBADOPERATION. If the capability is unavailable because of a dependency on another capability (i.e., ICAP_CCITTKFACTOR is not available unless ICAP_COMPRESSION is TWCP_GROUP32D), then return TWCC_CAPSEQERROR. Returning these condition codes makes it possible for an application using its own UI to intelligently make dependent capabilities available or unavailable for user access.

If the request was fulfilled, return TWRC_SUCCESS.

If the requested value is close to an acceptable value but doesn’t match exactly, set it as closely as possible and then return TWRC_CHECKSTATUS.

A Source support MSG_SET operations using the same containers it returns through MSG_GET, MSG_GETCURRENT and MSG_GETDEFAULT operations.

• Example #1, a call to DG_CONTROL / DAT_CAPABILITY / MSG_GET returns a TW_ENUMERTION container. The application changes the CurrentIndex and uses DG_CONTROL / DAT_CAPABILITY / MSG_SET to update the capability.


• Example #2, a call to DG_CONTROL / DAT_CAPABILITY / MSG_GET returns a TW_RANGE container. The application changes the CurrentValue and uses DG_CONTROL / DAT_CAPABILITY / MSG_SET to update the capability.

This does not imply or require support for constraining capabilities, the Source is only obligated to update the current value of the capability. If the Source does not support constraints for a capability, and the constraining values have been changed by the application, then the Source should apply the current value according to its own constraints, and if that value is valid, return TWRC_CHECKSTATUS to alert that application that it needs to do a MSG_GET to validate its changes.

• Example #3, if a Source supports the following range for ICAP_BRIGHTNESS: -1000.0 to -1000.0 in steps of 20.0, and if the current value is 0.0, then a call to DG_CONTROL / DAT_CAPABILITY / MSG_SET results in the following:twrange.ItemType = TWTY_FIX32twrange.MinValue = -1000.0twrange.MaxValue = 1000.0twrange.StepSize = 20.0twrange.DefaultValue = 0.0twrange.CurrentValue = 0.0

If the application sets twrange.CurrentValue to 900.0 and sends this structure to the Source using DG_CONTROL / DAT_CAPABILITY / MSG_SET, the call succeeds and returns TWRC_SUCCESS.If the application sets both twrange.CurrentValue and twrange.MaxValue to 900.0, then the status return depends on the Source. A Source that supports constaints accepts the new value and limits MaxValue to 900.0. A Source that does not support contraints accepts the value 900.0, because it falls in the range of -1000 to 1000, step 20; but it returns TWRC_CHECKSTATUS because it was unable to accept the request to limit MaxValue to 900.0.

Memory Allocation

The TW_CAPABILITY structure used in capability negotiation is both allocated and deallocated by the application. The Container structure pointed to by the hContainer field in TW_CAPABILITY is allocated by the Source for “get” operations (MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, MSG_RESET) and by the application for the MSG_SET operation. Regardless of which one allocates the container, the application is responsible for deallocating it when it is done with it.

Limitations Imposed by the Negotiation

If a Source agrees to allow an application to restrict a capability, it is critical that the Source abide by that agreement. If at all possible, the Source’s user interface should reflect the agreement and not offer invalid options. The Source should never transfer data that violates the agreement reached during capability negotiation. In that situation, the Source can decide to fail the transfer or somehow adjust the values.


Chapter 5

Data Transfers

Transfer Modes

All Sources must support Native and Buffered Memory data transfers. It is strongly suggested that they support Disk File mode, too. The default mode is Native. To select one of the other modes, the application must negotiate the ICAP_XFERMECH capability (whose default is TWSX_NATIVE). Sources must support negotiation of this capability. The native format for Microsoft Windows is DIB. For Macintosh, the native format is a PICT. The version of PICT to be transferred is the latest version available on the machine on which the application is running (usually PICT II for machines running 32-bit/color QuickDraw and PICT I for machines running black and white QuickDraw).

Initiating a Transfer

Transfers are initiated by the application (using the DG_IMAGE / DAT_IMAGExxxxFER / MSG_GET operations). A successful transfer transitions the session to State 7. If the transfer fails, the Source returns TWRC_FAILURE with the appropriate Condition Code and remains in State 6.

Concluding a Successful Transfer

To signal that the transfer is complete (i.e. the file is completed or the last buffer filled), the Source should return TWRC_XFERDONE. In response, the application must send a DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation. Only then may the Source transition from State 7 back to State 6 or to State 5 if no more images are ready to be transferred.

If more images are pending transfer, the Source must wait in State 6 until the application either requests the transfer or aborts the transfers. The Source may not “time-out” on any TWAIN transaction.

Aborting a Transfer

Either the application or Source can originate the termination of a transfer (although the application cannot do this in the middle of a Native or Disk File mode transfer). The Source generally terminates the transfer if the user cancels the transfer or a device error occurs which the Source determines is fatal to the transfer or the connection with the application. If the user canceled the transfer, the Source should return TWRC_CANCEL to signal the premature termination. The session remains in State 7 until the application sends the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER operation. If the Source aborts the transfer, it returns TWRC_FAILURE and the session typically remains in State 6. (If the failure occurs during the second buffer, or a later buffer, of a Buffered Memory transfer, the session remains in State 7.)

Native Mode Transfers

On Native mode transfers, the data parameter in the DSM_Entry call is a pointer to a variable of type TW_UINT32.


On Windows

The low word of this 32-bit integer is a handle variable to a DIB (Device Independent Bitmap) located in memory.

On Macintosh

This 32-bit integer is a handle to a Picture (a PicHandle). It is a Quick Draw picture located in memory.

Native transfers require the data to be transferred to a single large block of RAM. Therefore, they always face the risk of having an inadequate amount of RAM available to perform the transfer successfully.

If inadequate memory prevents the transfer, the Source has these options:

• Fail the transfer operation- Return TWRC_FAILURE / TWCC_LOWMEMORY

• Allow the user to clip the data to fit into available memory - Return TWRC_XFERDONE

• Allow the user to cancel the operation - Return TWRC_CANCEL

If the operation fails, the session remains in State 6. If the operation is canceled, the session remains in State 7 awaiting the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER or MSG_RESET from the application. The application can return the session to State 4 and attempt to renegotiate the transfer mechanism (ICAP_XFERMECH) to Disk File or Buffered Memory mode.

The Source cannot be interrupted by the application when it is acquiring an image through Native Mode Transfer. The Source’s user interface may allow the user to abort the transfer, but the application will not be able to do so even if the application presents its own acquisition user interface.

Disk File Mode Transfers

The Source selects a default file format and file name (typically, TWAIN.TMP in the current directory). It reports this information to the application in response to the DG_CONTROL / DAT_SETUPFILEXFER / MSG_GET.

The application may determine all of the Source’s supported file formats by using the ICAP_IMAGEFILEFORMAT capability. Based on this information, the application can request a particular file format and define its own choice of file name for the transfer. The desired file format and file name will be communicated to the Source in a DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET.

When the Source receives the DG_IMAGE / DAT_IMAGEFILEXFER / MSG_SET operation, it should transfer the data into the designated file. The following conditions may exist:

Condition How to Handle

No file name and/or file format was specified by the application during setup

Use either the Source’s default file name or the last file information given to the Source by the application. Create the file.


Chapter 5

The Source cannot be interrupted by the application when it is acquiring a file. The Source’s user interface may allow the user to abort the transfer, but the application will not be able to do so even if the application presents its own acquisition user interface.

Buffered Memory Mode Transfers

When the Source transfers strips of data, the application allocates and deallocates buffers used for a Buffered Memory mode transfer. However, the Source must recommend appropriate sizes for those buffers and should check that the application has followed its recommendations.

When the Source transfers tiles of data, the Source allocates the buffers. The application is responsible for deallocating the memory.

To determine the Source’s recommendations for buffer sizes, the application performs a DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation. The Source fills in the MinBufSize, MaxBufSize, and Preferred fields to communicate its buffer recommendations. Buffers must be double-word aligned and padded with zeros per raster line.

When an application issues a DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation, check the TW_IMAGEMEMXFER.Memory.Length field to determine the size of the buffer being presented to you. If it does not fit the recommendations, fail the operation with TWRC_FAILURE / TWCC_BADVALUE.

If the buffer is an appropriate size, fill in the required information.

• Sources must write one or more complete lines of image data (the full width of a strip or tile) into the buffer. Partial lines of image data are not allowed. If some of the buffer is unused, fill it in with zeros. Additionally, each line must be aligned to a 32-bit boundary. Return TWRC_SUCCESS after each successful buffer except for the last one (return TWRC_XFERDONE after that one).

• If the Source is transferring data whose bit depth is not 8 bits, it should fill the buffer without padding the data. If a 5-bit device wants the application to interpret its data as 8-bit data, it should report that it is supplying 8-bit data, make the valid data bits the most significant bits in the data byte, and pad the least significant bits with bits of whichever sense is “lightest”. Otherwise, the Source should pack the data bits together. For a 5-bit R-G-B device, that means the data for the green channel should immediately follow the last bit of the red channel. The application is responsible for “unpacking” the data. The Source reports how many bits it is providing per pixel in the BitsPerPixel field of the TW_IMAGEINFO data structure.

The application specified a file but failed to create it

Create the application’s defined file.

The application’s specified file exists but has data in it

Overwrite the existing data.

Condition How to Handle


Error Handling

Operation Triplet and State Verification

• Sources support all defined TWAIN triplets. A Source must verify every operation triplet they receive. If the operation is not recognized, the Source should return TWRC_FAILURE and TWCC_BADPROTOCOL.

• Sources must also maintain an awareness of what state their session is in. If an application invokes an operation that is invalid in the current state, the Source should fail the operation and return TWRC_FAILURE and TWCC_SEQERROR. Valid states for each operation are listed in Chapter 7, "Operation Triplets.”

• Anytime a Source fails an operation that would normally cause the session to transition to another state, the session should not transition but should remain in the original state.

• Each triplet operation has its own set of valid Return and Condition Codes as listed in Chapter 7, "Operation Triplets”. The Source must return a valid Return Code and set a valid Condition Code, if applicable, following every operation.

• All Return Codes and Condition Codes in the Source should be cleared upon the next call to DS_Entry( ). Clearing is delayed when a DG_CONTROL / DAT_STATUS / MSG_GET operation is received. In this case, the Source will fill the TW_STATUS structure with the current condition information and then clear that information.

• If an application attempts to connect to a Source that only supports single connection (or a multiply-connected Source that can’t establish any new connections), the Source should respond with TWRC_FAILURE and TWCC_MAXCONNECTIONS.

• For Windows Sources only, the DLL implementation makes it possible to be connected to more than one application. Unless the operation request is to open the Source, the Source must verify the application originating an operation is currently connected to the Source. To do this:

The Source must maintain a list containing the Id value for each connected application. (The Id value comes from the application’s TW_IDENTITY structure which is referenced by the pOrigin parameter in the DS_Entry( ) call.)

The Source should check the TW_IDENTITY.Id information of the application sending the operation and verify that it appears in the Source’s list of connected applications.

• For Windows only, if connected to multiple applications, the Source is responsible for maintaining a separate, current Condition Code for each application it is connected to. The Source writer should also maintain a temporary, and separate, Condition Code for any application that is attempting to establish a connection with the Source. This is true both for Sources that support only a single connection or have reached the maximum connections.

Unrecoverable Error Situations

The Source is solely responsible for determining whether an error condition within the Source is recoverable or not. The Source must determine when, and what, error condition information to present to the user. The application relies on the Source to specify when a failure occurs. If a Source is in an unrecoverable error situation, it may send a MSG_CLOSEDSREQ to the application to request to have its user interface disabled and have an opportunity to begin again.


Chapter 5

DAT_EVENT Handling Errors

One of the most common problems between a data source and application is the management of DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT. The symptoms are not immediately obvious, so it is worth mentioning them to assist new developers in quickly identifying and solving the problem.

Cannot use TAB or Keyboard Shortcuts to Navigate TWAIN DialogThe cause of this can be one of two things. Either the application is not forwarding all messages to TWAIN through the DAT_EVENT mechanism, or the data source is not properly processing the DAT_EVENT messages. (Windows: calling IsDialogMessage for each forwarded message with TWAIN Dialog handle)

TWAIN Dialog Box Combo Boxes cannot be opened, Edit boxes produce multiple chars per keystrokeThis case is caused by processing TWAIN Dialog Messages twice. Either the data source has not returned the proper return code in response to DAT_EVENT calls (Windows: TWRC_DSEVENT when IsDialogMessage returns TRUE), or the application is ignoring the return code.


This is not a problem when data source operates through TWAIN ThunkerProblems with the application handling of these messages are not often detected if the data source is operating through the TWAIN Thunking mechanism. This is because the Thunker process has a separate Window and Message pump that properly dispatch DAT_EVENT messages to the data source. Any mistake in application handling will pass without notice since all DAT_EVENT calls will return TWRC_NOTDSEVENT. (with the exception of important messages such as MSG_XFERREADY.)

Problem seems erratic, keyboard shortcuts and Tab key work for Message Boxes, but not TWAIN DialogThis observation often further confuses the issue. In Windows, a standard Message box is Modal, and operates from a local message pump until the user closes it. All messages are properly dispatched to the message box since it does not rely on the application message pump. The TWAIN Dialog is slightly different since it is implemented Modeless. There is no easy way to duplicate Modal behavior for the TWAIN Dialog.

Memory Management

Windows Specifics

On 16-bit Windows systems, a single copy of the Source Manager and Source(s) services all applications wishing to access TWAIN functionality. If the Source can connect to more than one application, it will probably need to maintain a separate execution frame for each connected application. The Source does not have unlimited memory available to it so be conservative in its use.

On 32-bit Windows systems, a new in-memory copy of the Source Manager and Source(s) is created in the Application’s calling space. In addition, a call may be made to the Windows On Windows (WOW) system, to support the thunking mechanism. For more information on the thunker, refer to Chapter 3, "Application Implementation.”

It is valid for an application to open a Source and leave it open between several acquires. Therefore, Sources should minimize the time and resources required to load and remain open (in State 4). Also, Sources should allow a reasonable number of connections to ensure they can handle more than one application using the Source in this manner (leaving it open between acquires).

Macintosh Specifics

Each application that loads the Source Manager has a private copy of the Source. Each Source that is connected also runs as a private copy. It is important for the Source writer to recognize that their Source will be using the memory heap of the host application, not in its own heap. Therefore, the Source should be conscientious with allocation and deallocation of memory.


Chapter 5

General Guidelines

The following are some general guidelines:

• Check, when the Source is launched, to assure that enough memory space is available for adequate execution.

• Always verify that allocations were successful.

• Work with relocatable objects whenever possible - the heap you fragment is not your own.

• Deallocate temporary memory objects as soon as they are no longer needed.

• Maintain as small a non-operating memory footprint as can prudently be done - the Source will be “compatible” with more applications on more machines.

• Clean up after yourself. When about to be closed, deallocate all locally allocated RAM, eliminate any other objects on the heap, and prepare as appropriate to terminate.

Local Variables• The Source may allocate and maintain local variables and buffers. Remember that you are

borrowing RAM from the application so be efficient about how much RAM is allocated simultaneously.

Instances Where the Source Allocates Memory

In general, the application allocates all necessary structures and passes them to the Source. There are a few exceptions to this rule:

• The Source must create the container, pointed to by the hContainer field, needed to hold capability information on DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, or MSG_RESET operations. The application deallocates the container.

• The Source allocates the buffer for Native mode data transfers. The application deallocates the buffer.

• Normally, the application creates the buffers used in a Buffered Memory transfer (DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET). However, if the Source is transferring tiled data, rather than strips of data, it is responsible for allocating the buffers. The application deallocates the buffers.

See the DG_IMAGE / DAT_JPEGCOMPRESSION operations.

Requirements for a Source to be TWAIN-Compliant The following lists of triplets and capabilities map out the minimum required set of features that a Source must offer programmatically to be TWAIN compliant. Sources, though, are strongly encouraged to go beyond this list and implement as many of their capabilities as possible for programmatic access.

This list is organized by versions of TWAIN to help Source writers decide which version they wish to support. It is also intended for Applications writers, who can use this information to


identify the real level of TWAIN support provided by a Source if its reported version is not matched by the items in this list.

Requirements

TWAIN 1.91 Sources must support all TWAIN 1.9 required features and the following:

Operations

DG_CONTROL / DAT_CAPABILITY / MSG_RESETALL


Operations

To be compliant with TWAIN 1.9 and higher, all Sources must support both UI and programmatic control. UI control is the traditional method of control used when an Application enables a Source with DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS (ShowUI == TRUE). Programmatic control implies that an Application will not use a Source’s UI, but will control it directly (ShowUI == FALSE). Application writers have long requested the ability to programmatically control Sources, so that they can present their own UI’s, offering the user a common look and feel no matter what Source is currently in use.

DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDSUIONLY – this operation is only required for mid- and high-volume scanners. It is strongly recommended for other devices since it allows a way for an application to create predefined session setups for devices that also include settings for custom features. Note that applications that support this operation must also support DAT_CUSTOMDSDATA.

DG_CONTROL / DAT_CAPABILITY / MSG_QUERYSUPPORT – This triplet was introduced in 1.7, and is now a required operation .

If DG_CONTROL / DAT_EXTIMAGEINFO is supported, then the following TWEI_ values must be reported:

TWEI_DOCUMENTNUMBERTWEI_PAGENUMBERTWEI_CAMERATWEI_FRAMENUMBERTWEI_FRAMETWEI_PIXELFLAVOR

If DG_AUDIO is supported, then ACAP_XFERMECH must be available.

Capabilities

CAP_UICONTROLLABLE – Sources must provide the ability to run without their internal GUI, which means that this capability must report TRUE.


No new requirements were added in this version.


Chapter 5


Operations

DG_CONTROL / DAT_CAPABILITY / MSG_QUERYSUPPORT – This triplet was introduced in 1.7, and should have been made mandatory, but was not. Sources that support 1.7 are strongly encouraged to support this operation, but it is not a mandatory requirement.


Capabilities

CAP_DEVICEONLINE – This capability is required to physically prove that the device is powered up and available.

TWAIN 1.5 Sources must support the following:

Operations


DG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENT

DG_CONTROL / DAT_CAPABILITY / MSG_GETDEFAULT

DG_CONTROL / DAT_CAPABILITY / MSG_RESET



DG_CONTROL / DAT_IDENTITY / MSG_GET




DG_CONTROL / DAT_PENDINGXFERS / MSG_GET

DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET

DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET




DG_CONTROL / DAT_XFERGROUP / MSG_GET


DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULT

DG_IMAGE / DAT_IMAGELAYOUT / MSG_RESET

DG_IMAGE / DAT_IMAGELAYOUT / MSG_SET


DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET


Capabilities

CAP_SUPPORTEDCAPS MSG_GET required

CAP_UICONTROLLABLE MSG_GET required

CAP_XFERCOUNT All MSG_* operations required

ICAP_COMPRESSION All MSG_GET* operations required

ICAP_BITDEPTH All MSG_* operations required

ICAP_BITORDER All MSG_* operations required

ICAP_PLANARCHUNKY All MSG_GET* operations required

ICAP_PHYSICALHEIGHT All MSG_GET* operations required

ICAP_PHYSICALWIDTH All MSG_GET* operations required

ICAP_PIXELFLAVOR All MSG_GET* operations required

ICAP_PIXELTYPE All MSG_* operations required

ICAP_UNITS All MSG_* operations required

ICAP_XFERMECH All MSG_* operations required

ICAP_XRESOLUTION All MSG_* operations required

ICAP_YRESOLUTION All MSG_* operations required

All Sources must implement the advertised features supported by their devices. They must make these features available to applications via the TWAIN protocol. For example, a Source that’s connected to a device that has an ADF must support DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT on:

CAP_FEEDERENABLEDCAP_FEEDERLOADED

and DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT,MSG_GETDEFAULT, MSG_RESET and MSG_SET on:

CAP_AUTOFEED

If the ADF also supports ejecting and rewinding of pages, then the Source should also support DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, MSG_RESET and MSG_SET on:

CAP_CLEARPAGECAP_REWINDPAGE

Application requirements for TWAIN-compliance are presented in Chapter 5, "Source Implementation.”


Chapter 5

Other Topics

Custom Operations

Manufacturers may add custom operations to their Sources. These can also be made known to application manufacturers. This mechanism allows an application to access functionality not normally available from a generic TWAIN Source.

One use of this mechanism might be to implement device-specific diagnostics for a hardware diagnostic program. These custom operations should be used sparingly and never in place of pre-defined TWAIN operations.

Custom operations are defined by specifying special values for Data Groups (DGs), Data Argument Types (DATs), Messages (MSGs), and Capabilities (CAPs). The following areas have been reserved for custom definitions:

The responsibility for naming and managing the use of custom designators lies wholly upon the TWAIN element originating the designator and the element consuming it. Prior to interpreting a custom designator, the consuming element must check the originating element’s ProductName string from its TW_IDENTITY structure. Since custom operation numbers may overlap, this is the only way to insure against confusion.

Networking

If a Source supports connection to a remote device over a network, the Source is responsible for hiding the network dependencies of that device’s operation from the application. The Source Manager does not know anything about networks.

In a networking situation, the Source will probably be built in two segments: One running on the machine local to the application, the other running remotely across the network. Sources are required to handle all the network interfacing with remote devices (real or logical) through local Source “stubs” that understand how to access both the network and the remote Source while interacting logically with the Source Manager.

The segment running on the local machine will probably be a “stub” Source. That is, the local stub will translate all operations received from the application and Source Manager into a form the remote source understands (that is, not necessarily TWAIN-defined operations). The stub also:

• Converts the information returned from the remote source into TWAIN-compliant results

• Handles local memory management for data copies and data transferring

Data Groups Top 8 bit flags (bits 24 - 31) in the DG identifiers reserved for custom use.

DATs Designators with values greater than 8000 hex.

Messages Designators with values greater than 8000 hex.

Capabilities Designators with values greater than 8000 hex.


• Isolates the network from the Source Manager and application

• Manages the connection with the remote Source

• Provides any needed code to handle local hardware (such as interface hardware)

• Provides the local user interface to control the remote Source


Chapter 5


6Entry Points and Triplet Components

Chapter ContentsEntry Points . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-1Data Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Data Argument Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-4Messages . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-6Custom Components of Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6-7

Entry PointsTWAIN has two entry points:

• DSM_Entry( ) - located in the Source Manager and typically called by applications, with the following exceptions where a Windows Source calls the Source Manager to communicate with an Application:

DG_CONTROL / DAT_NULL / MSG_XFERREADYDG_CONTROL / DAT_NULL / MSG_CLOSEDSREQDG_CONTROL / DAT_NULL / MSG_CLOSEDSOKDG_CONTROL / DAT_NULL / MSG_DEVICEEVENT

• DS_Entry( ) - located in the Source and called only by the Source Manager.

Programming Basics• Upon entry, the parameters must be ordered on the stack in Pascal form. Be sure that your

code expects this ordering rather than the reverse order that C uses.

• The keyword FAR is included in the entry point syntax to accommodate the 16-bit Windows segmented addressing scheme. It has no value for any other operating system, and is defined as an empty value for everything, except 16-bit Windows.

Data Flags and Data Groups

Versions of the TWAIN Specification up to and including TWAIN 2.0 indicate that the high 8-bits (24 – 31) in the TW_IDENTITY.SupportedGroups are reserved for custom use.


Chapter 6

TWAIN 2.0 has taken these bits for use by the Data Flags (DF_APP2, DF_DSM2 and DF_DS2). This breaks backwards capability with previous versions of the Specification. The risk is considered to be very low, since very few Sources or Applications work with these bits. However, the conflict can be managed in the following ways.

• Avoid the use of 0x10000000, 0x20000000 and 0x40000000, these correspond to DF_DSM2, DF_APP2 and DF_DS2. The remaining bits: 0x01000000, 0x02000000, 0x04000000, 0x08000000 and 0x80000000 are still in the custom space for Applications and Sources, and they will remain free for that use in all subsequent versions of TWAIN.

• Applications can modify their code to recognize when these bits are in use by a particular Source, which has always been a necessary pre-requisite for custom features, since the bits are guaranteed to have different meaning for different vendors.

• These flags are of most interest to the Data Source Manager, which is now open source (they dictate when DAT_ENTRYPOINT is called). If a legacy driver is using one of the custom bits, then propose a possible work-around to the TWAIN Working Group.

Declaration of DSM_Entry( )

Written in C code form, the declaration looks like this:

On Windows

TW_UINT16 FAR PASCAL DSM_Entry ( pTW_IDENTITY pOrigin, // source of message pTW_IDENTITY pDest, // destination of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

On Macintosh

FAR PASCAL TW_UINT16 DSM_Entry ( pTW_IDENTITY pOrigin, // source of message pTW_IDENTITY pDest, // destination of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

Parameters of DSM_Entry( )

pOrigin

This points to a TW_IDENTITY structure, allocated by the application, that describes the application making the call. One of the fields in this structure, called Id, is an arbitrary and unique identifier assigned by the Source Manager to tag the application as a unique TWAIN entity. The Source Manager maintains a copy of the application’s identity structure, so the application must not modify that structure unless it first breaks its connection with the Source Manager, then reconnects to cause the Source Manager to store the new, modified identity.


pDest

This is set either to NULL if the application is aiming the operation at the Source Manager or to the TW_IDENTITY structure of the Source that the application is attempting to reach. The application allocated the space for the Source’s identity structure when it decided which Source was to be connected. The Source’s TW_IDENTITY.Id is also uniquely set by the Source Manager when the Source is opened and should not be modified by the Source. The application should not count on the value of this field being consistent from one session to the next because the Source Manager reallocates these numbers every time it is opened. The Source Manager keeps a copy of the Source’s identity structure as should the application and the Source.

DG

The Data Group of the operation triplet. Currently, only DG_CONTROL, DG_IMAGE, and DG_AUDIO are defined.

DAT

The Data Argument Type of the operation triplet. A complete list appears later in this chapter.

MSG

The Message of the operation triplet. A complete list appears later in this chapter.

pData

The pData parameter is of type TW_MEMREF and is a pointer to the data (a variable or, more typically, a structure) that will be used according to the action specified by the operation triplet.

Declaration of DS_Entry( )

DS_Entry is only called by the Source Manager. Written in C code form, the declaration looks like this:

On Windows

TW_UINT16 FAR PASCAL DS_Entry ( pTW_IDENTITY pOrigin, // source of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx TW_MEMREF pData // pointer to data );

On Macintosh

FAR PASCAL TW_UINT16 DS_Entry ( pTW_IDENTITY pOrigin, // source of message TW_UINT32 DG, // data group ID: DG_xxxx TW_UINT16 DAT, // data argument type: DAT_xxxx TW_UINT16 MSG, // message ID: MSG_xxxx


Chapter 6

TW_MEMREF pData // pointer to data );

Data GroupsTWAIN operations can be broadly classified into three data groups:

Control Oriented (DG_CONTROL)Controls the TWAIN session. Consumed by both Source Manager and Source. It is always available, no matter what the current setting of DG_CONTROL / DAT_XFERGROUP.

Image Data Oriented (DG_IMAGE)

Indicates the kind of data to be transferred. Change between DG_AUDIO and DG_IMAGE as needed using DG_CONTROL / DAT_XFERGROUP / MSG_SET. The default at startup is for a Source to be ready to transfer DG_IMAGE data.

Audio Data Oriented (DG_AUDIO)

Indicates the kind of data to be transferred. Change between DG_AUDIO and DG_IMAGE as needed using DG_CONTROL / DAT_XFERGROUP / MSG_SET.

Currently, only image and audio data are supported but this could be expanded to include text, etc. This has several future implications. If more than one data type exists, an application and a Source will need to decide what type(s) of data the Source can, and will be allowed to, produce before a transfer can occur. Further, if multiple transfers are being generated from a single acquisition—such as when image and text are intermixed and captured from the same page—it must be unambiguous which type of data is being returned from each data transfer.

Programming Basics

Note the following:

• Data Group designators are 32-bit, unsigned values. The actual values that are assigned are powers of two (bit flags) so that the DGs can be easily masked.

• There are 24 DGs designated as reserved for pre-defined DGs . Four are currently in use. The top 8 bits are reserved for custom DGs.

Data Argument TypesData Argument Types, or DATs, are used to allow programmatic identification of the TWAIN type for the structure of status variable referenced by the entry point parameter pData. pData will always point to a variable or data structure defined by TWAIN. If the consuming application or Source switches (cases, etc.) on the DAT specified in the formal parameter list of the entry point call, it can handle the form of the referenced data correctly.


Data Type Used by Associated structure or type

DAT_NULL ANY DG Null structure. No data required for the operation

DAT_CUSTOMBASE n/a Not a DAT in itself, but the baseline a Source must use when creating a custom DAT.

DAT_AUDIOFILEXFER DG_AUDIO Operates on null data. Filename / Format already negotiated.

DAT_AUDIONATIVEXFER DG_AUDIO TW_UINT32

On Windows - low word = WAV handleOn Macintosh - audio handle

DAT_CAPABILITY DG_CONTROL TW_CAPABILITY structure

DAT_ENTRYPOINT DG_CONTROL TW_ENTRYPOINT structure

DAT_EVENT DG_CONTROL TW_EVENT structure

DAT_FILESYSTEM DG_CONTROL TW_FILESYSTEM structure

DAT_IDENTITY DG_CONTROL TW_IDENTITY structure

DAT_PARENT DG_CONTROL TW_INT32

On Windows - low word=Window handleOn Macintosh - Set to NULL

DAT_PASSTHRU DG_CONTROL TW_PASSTHRU structure

DAT_PENDINGXFERS DG_CONTROL TW_PENDINGXFERS structure

DAT_SETUPFILEXFER DG_CONTROL TW_SETUPFILEXFER structure

DAT_SETUPMEMXFER DG_CONTROL TW_SETUPMEMXFER structure

DAT_STATUS DG_CONTROL TW_STATUS structure

DAT_USERINTERFACE DG_CONTROL TW_USERINTERFACE structure

DAT_XFERGROUP DG_CONTROL TW_UINT32

A DG designator describing data to be transferred (currently only image data is supported)

DAT_CIECOLOR DG_IMAGE TW_CIECOLOR structure

DAT_GRAYRESPONSE DG_IMAGE TW_GRAYRESPONSE structure

DAT_IMAGEFILEXFER DG_IMAGE Operates on NULL data. Filename/Format already negotiated

DAT_IMAGEINFO DG_IMAGE TW_IMAGEINFO structure

DAT_IMAGELAYOUT DG_IMAGE TW_IMAGELAYOUT structure

DAT_IMAGEMEMXFER DG_IMAGE TW_IMAGEMEMXFER structure

DAT_IMAGEMEMFILEXFER DG_IMAGE TW_IMAGEMEMXFER structure


Chapter 6

MessagesA Message, or MSG, is used to communicate between TWAIN elements what action is to be taken upon a particular piece of data, or for a data-less operation, what action to perform. If an application wants to make anything happen in, or inquire any information from, a Source or the Source Manager, it must make a call to DSM_Entry( ) with the proper MSG as one parameter of the operation triplet. The data to be acted upon is also specified in the parameter list of this call.

A MSG is always associated with a Data Group (DG) identifier and a Data Argument Type (DAT) identifier in an operation triplet. This operation unambiguously specifies what action is to be taken on what data. Refer to Chapter 7, "Operation Triplets” for the list of defined operation triplets.

DAT_IMAGENATIVEXFER DG_IMAGE TW_UINT32;On Windows - low word=DIB handleOn Macintosh - PicHandle

DAT_JPEGCOMPRESSION DG_IMAGE TW_JPEGCOMPRESSION structure

DAT_PALETTE8 DG_IMAGE TW_PALETTE8 structure

DAT_RGBRESPONSE DG_IMAGE TW_RGBRESPONSE structure

Message ID Valid DAT(s) Description of Specified Action

MSG_AUTOMATICCAPTUREDIRECTORY

DAT_FILESYSTEM Place to store images acquired during automatic capture

MSG_CHANGEDIRECTORY DAT_FILESYSTEM Change device, domain, host, or image directory

MSG_CLOSEDS DAT_IDENTITY Close the specified Source

MSG_CLOSEDSM DAT_PARENT Close the Source Manager

MSG_CLOSEDSREQ DAT_NULL Source requests for application to close Source

MSG_COPY DAT_FILESYSTEM Copy images across storage devices

MSG_CREATEDIRECTORY DAT_FILESYSTEM Create an image directory

MSG_CUSTOMBASE n/a Not a message in itself, but the baseline a Source must use when creating a custom message

MSG_DELETE DAT_FILESYSTEM Delete an image or an image directory

MSG_DEVICEEVENT DAT_NULL Report an event from the Source to the Source Manager

MSG_DISABLEDS DAT_USERINTERFACE Disable data transfer in the Source

MSG_ENABLEDS DAT_USERINTERFACE Enable data transfer in the Source

Data Type Used by Associated structure or type


Custom Components of Triplets

Custom Data Groups

A manufacturer may choose to implement custom data descriptors that require a new Data Group. This would be needed if someone decides to extend TWAIN to, say, satellite telemetry.

• The top 8 bits of every DG_xxxx identifier are reserved for use as custom DGs. Custom DG identifiers must use one of the upper 8 bits of the DG_xxxx identifier. Remember, DGs are bit flags.

MSG_ENDXFER DAT_PENDINGXFERS Application tells Source that transfer is over

MSG_FORMATMEDIA DAT_FILESYSTEM Format a storage device

MSG_GET various DATs Get all Available Values including Current & Default

MSG_GETCLOSE DAT_FILESYSTEM Close a file context created by MSG_GETFIRSTFILE

MSG_GETCURRENT various DATs Get Current value

MSG_GETDEFAULT various DATs Get Source’s preferred default value

MSG_GETFIRST DAT_IDENTITY Get first element from a “list”

MSG_GETFIRSTFILE DAT_FILESYSTEM Get the first file in a directory

MSG_GETINFO DAT_FILESYSTEM Get information about the current file

MSG_GETNEXT DAT_IDENTITY Get next element from a “list”

MSG_GETNEXTFILE DAT_FILESYSTEM Get the next file in a directory

MSG_NULL None No action to be taken

MSG_OPENDS DAT_IDENTITY Open and Initialize the specified Source

MSG_OPENDSM DAT_PARENT Open the Source Manager

MSG_PASSTHRU DAT_PASSTHRU For use by Source Vendors only

MSG_PROCESSEVENT DAT_EVENT Tells Source to check if event/message belongs to it

MSG_RENAME DAT_FILESYSTEM Rename an image or an image directory

MSG_RESET various DATs Return specified item to power-on (TWAIN default) condition

MSG_SET various DATs Set one or more values

MSG_USERSELECT DAT_IDENTITY Presents dialog of all Sources to select from

MSG_XFERREADY DAT_NULL The Source has data ready for transfer to the application

Message ID Valid DAT(s) Description of Specified Action


Chapter 6

• The originator of the custom DG must fill the ProductName field in the application or Source’s TW_IDENTITY structure with a uniquely descriptive name. The consumer will look at this field to determine whose custom DG is being used.

• TWAIN provides no formal allocation (or vendor-specific “identifier blocks”) for custom data group identifiers nor does it do any coordination to avoid collisions.

• The DG_CUSTOMBASE value resides in the TWAIN.H file. All custom IDs must be numerically greater than this base. A similar custom base “address” is defined for Data Argument Types, Messages, Capabilities, Return Codes, and Condition Codes. The only difference in concept is that DGs are the only designators defined as bit flags. All other custom values can be any integer value larger than the xxxx_CUSTOMBASE defined for that type of designator.

Custom Data Argument Types

DAT_CUSTOMBASE is defined in the TWAIN.H file to allow a Source vendor to define “custom” DATs for their particular device(s). The application can recognize the Source by checking the TW_IDENTITY.ProductName and the TW_IDENTITY.TW_VERSION structure. If an application is aware that this particular Source offers custom DATs, it can use them. No changes to TWAIN or the Source Manager are required to support such identifiers (or the data structures which they imply).

Refer to the TWAIN.H file for the value of DAT_CUSTOMBASE for custom DATs. All custom values must be numerically greater than this constant.

Custom Messages

As with the DATs, MSG_CUSTOMBASE is included in TWAIN.H so that the Source writer can create custom messages specific to their Source. If the applications understand these custom messages, actions beyond those defined in this specification can be performed through the normal TWAIN mechanism. No modifications to TWAIN or the Source Manager are required.

Remember that the consumer of these custom values will look in your TW_IDENTITY.ProductName field to clarify what the identifier’s value means—there is no other protection for overlapping custom definitions. Refer to the TWAIN.H file for the value of MSG_CUSTOMBASE for custom Messages. All custom values must be numerically greater than this value.


7Operation Triplets

Chapter ContentsTriplet Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-1Format of the Operation Triplet Descriptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-5Operation Triplets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7-7

Triplet Overview

From Application to Source Manager (Control Information)

Data Group Data Argument Type Message Page

DG_CONTROL DAT_IDENTITY MSG_CLOSEDS 7-59

MSG_GETDEFAULT 7-62

MSG_GETFIRST 7-63

MSG_GETNEXT 7-65

MSG_OPENDS 7-67

MSG_SET 7-71

MSG_USERSELECT 7-72

DG_CONTROL DAT_PARENT MSG_CLOSEDSM 7-79

MSG_OPENDSM 7-80

DG_CONTROL DAT_STATUS MSG_GET 7-99


Chapter 7

From Application to Source (Control Information)


DG_CONTROL DAT_CAPABILITY MSG_GET 7-12

MSG_GETCURRENT 7-15

MSG_GETDEFAULT 7-18

MSG_GETHELP 7-21

MSG_GETLABEL 7-22

MSG_GETLABELENUM 7-23

MSG_QUERYSUPPORT 7-25

MSG_RESET 7-27

MSG_RESETALL 7-30

MSG_SET 7-32

DG_CONTROL DAT_CUSTOMDSDATA MSG_GET

MSG_SET

7-367-37

DG_CONTROL DAT_DEVICEEVENT MSG_GET 7-38

DG_CONTROL DAT_FILESYSTEM MSG_AUTOMATICCAPTURE DIRECTORY

7-43

MSG_CHANGEDIRECTORY 7-44

MSG_COPY 7-46

MSG_CREATEDIRECTORY 7-47

MSG_DELETE 7-49

MSG_FORMATMEDIA 7-51

MSG_GETCLOSE 7-52

MSG_GETFIRSTFILE 7-53

MSG_GETINFO 7-55

MSG_GETNEXTFILE 7-56

MSG_RENAME 7-58

DG_CONTROL DAT_EVENT MSG_PROCESSEVENT 7-41

DG_CONTROL DAT_PASSTHRU MSG_PASSTHRU 7-81

DG_CONTROL DAT_PENDINGXFERS MSG_ENDXFER 7-82

MSG_GET 7-84

MSG_RESET 7-86

MSG_STOPFEEDER 7-88


From Application to Source (Image Information)

DG_CONTROL DAT_SETUPFILEXFER MSG_GET 7-89

MSG_GETDEFAULT 7-91

MSG_RESET 7-93

MSG_SET 7-95

DG_CONTROL DAT_SETUPMEMXFER MSG_GET 7-97

DG_CONTROL DAT_STATUS MSG_GET 7-99

DG_CONTROL DAT_STATUSUTF8 MSG_GET 7-101

DG_CONTROL DAT_USERINTERFACE MSG_DISABLEDS

MSG_ENABLEDS

MSG_ENABLEDSUIONLY

7-1027-1047-107

MSG_ENABLEDS 7-104

MSG_ENABLEDSUIONLY 7-107

DG_CONTROL DAT_XFERGROUP MSG_GET 7-108

MSG_SET 7-109

Data Group Data Argument Type Message Page #

DG_IMAGE DAT_CIECOLOR MSG_GET 7-110

DG_IMAGE DAT_EXTIMAGEINFO MSG_GET 7-112

DG_IMAGE DAT_GRAYRESPONSE MSG_RESET 7-114

MSG_SET 7-115

DG_IMAGE DAT_ICCPROFILE MSG_GET 7-116

DG_IMAGE DAT_IMAGEFILEXFER MSG_GET 7-118

DG_IMAGE DAT_IMAGEINFO MSG_GET 7-120

DG_IMAGE DAT_IMAGELAYOUT MSG_GET 7-122

MSG_GETDEFAULT 7-124

MSG_RESET 7-125

MSG_SET 7-126

DG_IMAGE DAT_IMAGEMEMFILEXFER MSG_GET 7-118

DG_IMAGE DAT_IMAGEMEMXFER MSG_GET 7-128

DG_IMAGE DAT_IMAGEFILEXFER MSG_GET 7-128

DG_IMAGE DAT_IMAGENATIVEXFER MSG_GET 7-134



Chapter 7

From Application to Source (Audio Information)

From Source Manager to Source (Control Information)

From Source to Application (Control Information via the Source Manager)(Used by Windows Sources only

)

DG_IMAGE DAT_JPEGCOMPRESSION MSG_GET 7-137


MSG_RESET 7-140

MSG_SET 7-141

DG_IMAGE DAT_PALETTE8 MSG_GET 7-142


MSG_RESET 7-145

MSG_SET 7-146

DG_IMAGE DAT_RGBRESPONSE MSG_RESET 7-147

MSG_SET 7-149


DG_AUDIO DAT_AUDIOFILEXFER MSG_GET 7-7

DG_AUDIO DAT_AUDIOINFO MSG_GET 7-8

DG_AUDIO DAT_AUDIONATIVEXFER MSG_GET 7-9


DG_CONTROL DAT_IDENTITY MSG_CLOSEDS 7-59

MSG_GET 7-60

MSG_OPENDS 7-61


DG_CONTROL DAT_NULL MSG_CLOSEDSOK

MSG_CLOSEDSREQ 7-74

MSG_DEVICEEVENT 7-76

MSG_XFERREADY 7-77



TWAIN 2.0 (Entry Points)

Format of the Operation Triplet DescriptionsThe following pages describe the operation triplets. They are all included and are arranged in alphabetical order using the Data Group, Data Argument Type, and Message identifier list.

There are three operations that are duplicated because that have a different originator and/or destination in each case. They are:

• DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDS✔ from Application to Source Manager✔ from Source Manager to Source

• DG_CONTROL / DAT_IDENTITY / MSG_OPENDS✔ from Application to Source Manager✔ from Source Manager to Source

• DG_CONTROL / DAT_STATUS / MSG_GET✔ from Application to Source Manager✔ from Application to Source

The format of each page is:


DG_CONTROL DAT_ENTRYPOINT MSG_GET 7-39

MSG_SET 7-40


Chapter 7

Triplet - The Concise DG / DAT / MSG Information

Call

Actual format of the routine call (parameter list) for the operation. Identification of the data structure used for the pData parameter is included.

Valid States

The states in which the application, Source Manager, or Source may legally invoke the operation.

Description

General description of the operation.

Origin of the Operation (Application, Source Manager or, Source)

The action(s) the application, Source Manager, or Source should take before invoking the operation.

Destination of the Operation (Source Manager or Source)

The action that the destination element (Source Manager or Source) of the operation will take.

Return Codes

The Return Codes and Condition Codes that are defined and valid for this operation.

See Also

Lists other related operation triplets, capabilities, constants, etc.


Operation Triplets

DG_AUDIO / DAT_AUDIOFILEXFER / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_AUDIO, DAT_AUDIOFILEXFER, MSG_GET, NULL);

Valid States

6 (transitions to state 7)

Description

(Similar operation to DAT_IMAGEFILEXFER).

This operation is used to initiate the transfer of audio from the Source to the application via the disk-file transfer mechanism. It causes the transfer to begin.

No special set up or action required. Application should have already invoked the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation, unless the Source’s default transfer format and file name (typically, TWAINAUD.TMP) are acceptable to the application. The application need only invoke this operation once per image transferred.

Source should acquire the audio data, format it, create any appropriate header information, and write everything into the file specified by the previous DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation, and close the file.

Audio transfers are optional. If an application transfers only the images and never changes to DG_AUDIO, then the audio snippets will be automatically discarded or skipped by the Source.

Return Codes

TWRC_CANCEL

TWRC_XFERDONE

TWRC_FAILURE

TWCC_BADPROTOCOL.

TWCC_OPERATIONERROR

TWCC_SEQERROR - not state 6.

See Also

ACAP_XFERMECH


Chapter 7

DG_AUDIO / DAT_AUDIOINFO / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_AUDIO, DAT_AUDIOINFO, MSG_GET, pSourceAudioInfo);

pSourceAudioInfo = A pointer to a TW_AUDIOINFO structure

Valid States

6 and 7

Description

Used to get the information of the current audio data ready to transfer. (Similar operation to DAT_IMAGEINFO)

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL

TWCC_SEQERROR

See Also

-


DG_AUDIO / DAT_AUDIONATIVEXFER / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_AUDIO, DAT_AUDIONATIVEXFER, MSG_GET, pHandle);

pHandle = A pointer to a variable of type TW_UINT32

On Windows - This 32 bit integer is a handle variable to WAV data located in memory.

On Macintosh - This 32-bit integer is a handle to AIFF data

Valid States

6 (transitions to state 7)

Description

(Similar operation to DAT_IMAGENATIVEXFER).

Causes the transfer of an audioÆs data from the Source to the application, via the Native transfer mechanism, to begin. The resulting data is stored in main memory in a single block. The data is stored in AIFF format on the Macintosh and as a WAV format under Microsoft Windows. The size of the audio snippet that can be transferred is limited to the size of the memory block that can be allocated by the Source.

Note: This is the default transfer mechanism. All Sources support this mechanism if DG_AUDIO is supported. The Source will use this mechanism unless the application explicitly negotiates a different transfer mechanism with ACAP_XFERMECH.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL.


See Also

ACAP_XFERMECH


Chapter 7

DG_CONTROL / DAT_CALLBACK / MSG_INVOKE_CALLBACK

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_CALLBACK, MSG_INVOKE_CALLBACK, (TW_MEMREF)&callback);

Valid States

4, 5, 7 (depending on the message)

Description

This triplet is sent by the DS to the DSM, which in turn calls the application’s registered callback function. The last argument is a pointer to an initialized TW_CALLBACK structure, which contains the message to be processed.

The TW_CALLBACK structure should be initialized as follows:

Msg Initialized to any valid DG_CONTROL / DAT_NULL message.

The message specified will be processed in the same manner as the DAT_NULL mechanism employed by the Windows version. These are:

MSG_XFERREADY

MSG_CLOSEDSREQ

MSG_CLOSEDSOK

MSG_DEVICEEVENT

MSG_INVOKE_CALLBACK is the only way for a Mac OS X DS to inform the application of these events.

Return Codes

TWRC_FAILURE

See Also

DG_CONTROL / DAT_CALLBACK / MSG_REGISTER_CALLBACK


DG_CONTROL / DAT_CALLBACK / MSG_REGISTER_CALLBACK

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_CALLBACK, MSG_REGISTER_CALLBACK, (TW_MEMREF)&callback);

Valid States

4

Description

This triplet is sent to the DSM by the Application to register the application’s entry point with the DSM, so that the DSM can use callbacks to inform the application of events generated by the DS.

The last argument is a pointer to an initialized TW_CALLBACK structure. The TW_CALLBACK structure should be initialized as follows:

CallBackProc The callback function’s entry point, used by MSG_REGISTER_CALLBACK

RefCon An application defined reference constant

Return Codes

TWRC_FAILURE

See Also

DG_CONTROL / DAT_CALLBACK / MSG_INVOKE_CALLBACK


Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_GET, pCapability);

pCapability = A pointer to a TW_CAPABILITY structure.

Valid States

4 through 7

Description

Returns the Source’s Current, Default and Available Values for a specified capability.

These values reflect previous MSG_SET operations on the capability, or Source’s automatic changes. (See MSG_SET).

Note: This operation does not change the Current or Available Values of the capability.

Application

Set the pCapability fields as follows:

pCapability->Cap = the CAP_xxxx or ACAP_xxxx or ICAP_xxxx identifier

pCapability->ConType = TWON_DONTCARE16pCapability->hContainer = NULL

The Source will allocate the memory for the necessary container structure but the application must free it when the operation is complete and the application no longer needs to maintain the information.

Use MSG_GET:

• As the first step in negotiation of a capability’s Available Values.

• To check the results if a MSG_SET returns TWRC_CHECKSTATUS.

• To check the Available, Current and Default Values with one command.

This operation may fail for a low memory condition. Either recover from a TWCC_LOWMEMORY failure by freeing memory for the Source to use so it can continue, or terminating the acquisition and notifying the user of the low memory problem.

Source

If the application requests this operation on a capability your Source does not recognize (and you’re sure you’ve implemented all the capabilities that you’re required to), disregard the operation, but return TWRC_FAILURE with TWCC_BADCAP.


If you support the capability, fill in the fields listed below and allocate the container structure and place its handle into pCapability->hContainer. The container should be referenced by a “handle” of type TW_HANDLE.

Fill the fields in pCapability as follows:

pCapability->ConType = TWON_ARRAY,TWON_ONEVALUE,TWON_ENUMERATION, orTWON_RANGE

pCapability->hContainer = TW_HANDLE referencing a container of ConType

Set ConType to the container type your Source uses for this capability. For container types of TWON_ARRAY and TWON_ONEVALUE provide the Current Value. For container types TWON_ENUMERATION and TWON_RANGE provide the Current, Default and Available Values.

This is a memory allocation operation. It is possible for this operation to fail due to a low memory condition. Be sure to verify that the allocation is successful. If it is not, attempt to reduce the amount of memory occupied by the Source. If the allocation cannot be made, return TWRC_FAILURE with TWCC_LOWMEMORY to the application and set the pCapability->hContainer handle to NULL.

Note: The Source must be able to respond to an inquiry about any of its capabilities at any time that the Source is open.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADCAP /* Unknown capability--Source does not recognize */ /* this capability. This code should not be used */ /* by sources after 1.6. Applications still need */ /* to test for it for backward compatibility. */

TWCC_CAPUNSUPPORTED /* Capability not supported by source. Sources*/ /* 1.6 and newer must use this instead of */ /* using TWCC_BADCAP. */

TWCC_CAPBADOPERATION /* Operation not supported by capability.*/ /* Sources 1.6 and newer must use this */ /* instead of using TWCC_BADCAP.

TWCC_CAPSEQERROR /* Capability has dependency on other */ /* capability. Sources 1.6 and newer must */ /* use this instead of using TWCC_BADCAP. */

TWCC_BADDEST /* No such Source in session with */ /* application */

TWCC_LOWMEMORY /* Not enough memory to complete the */ /* operation */

TWCC_SEQERROR /* Operation invoked in invalid state */


Chapter 7

See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENT, MSG_GETDEFAULT, MSG_RESET, and MSG_SET

“Capability Constants” on page 8-74.

“Capability Containers” on page 2-17 and TW_ONEVALUE, TW_ENUMERATION, TW_RANGE, TW_ARRAY.

“The Capability Listings” on page 10-10.”


DG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENT

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_GETCURRENT, pCapability);


Valid States

4 through 7

Description

Returns the Source’s Current Value for the specified capability.

The Current Value reflects previous MSG_SET operations on the capability, or Source’s automatic changes. (See MSG_SET).

Note: This operation does not change the Current Values of the capability.

Application


pCapability->Cap = the CAP_xxxx or ACAP_xxxx or ICAP_xxxx identifierpCapability->ConType = TWON_DONTCARE16pCapability->hContainer = NULL


Use MSG_GETCURRENT:

• To check the Source’s power-on Current Values (see Chapter 10, "Capabilities” for TWAIN-defined defaults for each capability).

• To check just the Current Value (in place of using MSG_GET).

• In State 6 to determine the settings. They could have been set by the user (if TW_USERINTERFACE.ShowUI = TRUE) or be the results of automatic processes used by the Source.



Chapter 7

Source




pCapability->ConType = TWON_ARRAY or TWON_ONEVALUE


Set ConType to the container type that matches the type for this capability. Fill the fields in the container structure with the Current Value of the capability.

This is a memory allocation operation. It is possible for this operation to fail due to a low memory condition. Be sure to verify that the allocation is successful. If it is not, attempt to reduce the amount of memory occupied by the Source. If the allocation cannot be made, return TWRC_FAILURE with TWCC_LOWMEMORY to the application and set the pCapability->hContainer handle to NULL.

Note that the Source must be able to respond to an inquiry about any of its capabilities at any time that the Source is open.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



TWCC_CAPBADOPERATION /* Operation not supported by capability. */ /* Sources 1.6 and newer must use this instead*/ /* of using TWCC_BADCAP.

TWCC_CAPSEQERROR /* Capability has dependency on other */ /* capability. Sources 1.6 and newer must use */ /* this instead of using TWCC_BADCAP. */

TWCC_BADDEST /* No such Source in-session with */ /* application */


TWCC_SEQERROR /* Operation invoked in invalid state. */


See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETDEFAULT, MSG_RESET, and MSG_SET

Capability Constants (in Chapter 8, "Data Types and Data Structures”)

Capability Containers: TW_ONEVALUE, TW_ENUMERATION, TW_RANGE, TW_ARRAY (in Chapter 8, "Data Types and Data Structures”)

Listing of all capabilities (in Chapter 10, "Capabilities”).


Chapter 7

DG_CONTROL / DAT_CAPABILITY / MSG_GETDEFAULT

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_GETDEFAULT, pCapability);


Valid States

4 through 7

Description

Returns the Source’s Default Value. This is the Source’s preferred default value.

The Source’s Default Value cannot be changed.

Application




Use MSG_GETDEFAULT:

• To check the Source’s preferred Values. Using the Source’s preferred default as the Current Value may increase performance in some Sources.


Source

If the application requests this operation on a capability your Source does not recognize (and you are sure you have implemented all the capabilities that you’re required to), disregard the operation, but return TWRC_FAILURE with TWCC_BADCAP.


• Fill the fields in pCapability as follows:




Set ConType to the container type that matches for this capability. Fill the fields in the container with the Default Value of this capability.

The Default Value is the preferred value for the Source. This value is used as the power-on value for capabilities if TWAIN does not specify a default.

This is a memory allocation operation. It is possible for this operation to fail due to a low memory condition. Be sure to verify that the allocation is successful. If it is not, attempt to reduce the amount of memory occupied by the Source. If the allocation cannot be made return TWRC_FAILURE with TWCC_LOWMEMORY to the application and set the pCapability->hContainer handle to NULL.


Return Codes

TWRC_SUCCESS

TWRC_FAILURE








See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_RESET, and MSG_SET

Capability Constants (in Chapter 10, "Capabilities”)



Chapter 7

Listing of all capabilities (in Chapter 10, "Capabilities”)


DG_CONTROL / DAT_CAPABILITY / MSG_GETHELP

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_CAPABILITY, MSG_GETHELP, pTwCapability);

pTwCapability = A pointer to a TW_CAPABILITY structure.

Valid States

4

Description

Returns help text suitable for use in a GUI; for instance: “Specify the amount of detail in an image. Higher values result in more detail.” for ICAP_XRESOLUTION.

Source

The Source returns a TW_ONEVALUE container with a TW_STR4096 item type. The string data is UTF-8 encoded. The language is determined by the TW_IDENTITY.TW_VERSION.Language reported back by the Source, unless overridden by CAP_LANGUAGE.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_CAPUNSUPPORTED

See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GETLABEL


Chapter 7

DG_CONTROL / DAT_CAPABILITY / MSG_GETLABEL

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_CAPABILITY, MSG_GETLABEL, pTwCapability);


Valid States

4

Description

Returns a label suitable for use in a GUI, for instance “Resolution:” for ICAP_XRESOLUTION.

Source

The Source returns a TW_ONEVALUE container with a TW_STR255 item type. The string data is UTF-8 encoded. The language is determined by the TW_IDENTITY.TW_VERSION.Language reported back by the Source, unless overridden by CAP_LANGUAGE.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_CAPUNSUPPORTED

See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GETHELP


DG_CONTROL / DAT_CAPABILITY / MSG_GETLABELENUM

CallDSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_CAPABILITY, MSG_GETLABELENUM, pTwCapability);


Valid States4

Description

Return all of the labels for a capability of type TW_ARRAY or TW_ENUMERATION, for example “US Letter” for ICAP_SUPPORTEDSIZES’ TWSS_USLETTER.

Application

The Application receives a TW_ARRAY with a TW_STR255 type. Each index in the array corresponds to the same index of a TW_ARRAY or a TW_ENUMERATION returned by a MSG_GET for that same capability.

For example, if ICAP_SUPPORTEDSIZES returns the following for MSG_GET:

ptwenumeration->ItemType = TWTY_UINT16ptwenumeration->NumItems = 3ptwenumeration->CurrentIndex = 0ptwenumeration->DefaultIndex = 0((TW_UINT16*)&ptwenumeration->ItemList)[0] = TWSS_USLETTER((TW_UINT16*)&ptwenumeration->ItemList)[1] = TWSS_A4LEDGER((TW_UINT16*)&ptwenumeration->ItemList)[2] = TWSS_USEXECUTIVE

It should return something like the following for MSG_GETLABELENUM:

ptwarray->ItemType = TWTY_STR255ptwarray ->NumItems = 3((char*)&ptwarray->ItemList)[0*sizeof(TW_STR255)] is “US Letter”((char*)&ptwarray->ItemList)[1*sizeof(TW_STR255)] is “A4 Letter”((char*)&ptwarray->ItemList)[2*sizeof(TW_STR255)] is “US Executive”

Source

The Source returns a TW_ARRAY container with a TW_STR255 item type. The string data is UTF-8 encoded. The language is determined by the TW_IDENTITY.TW_VERSION.Language reported back by the Source, unless overridden by CAP_LANGUAGE.

This feature is only supported for capabilities that return TW_ARRAY or TW_ENUMERATION for MSG_GET. Other capabilities (like TW_RANGE or TW_ONEVALUE) return TWRC_FAILURE / TWCC_BADPROTOCOL.


Chapter 7

Return CodesTWRC_SUCCESS

TWRC_FAILURE

TWCC_CAPUNSUPPORTED TWCC_BADPROTOCOL

See AlsoDG_CONTROL / DAT_CAPABILITY / MSG_GETLABEL


DG_CONTROL / DAT_CAPABILITY / MSG_QUERYSUPPORT

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_QUERYSUPPORT, pCapability);


Valid States

4 through 7

Description

Returns the Source’s support status of this capability.

Application


pCapability->Cap = the CAP_xxxx or ACAP_xxxx or ICAP_xxxx identifierpCapability->ConType = TWON_ONEVALUEpCapability->hContainer = NULL


Use MSG_QUERYSUPPORT:

• To check the whether the Source supports a particular operation on the capability.


Source


pCapability->ConType = TWON_ONEVALUE

pCapability->hContainer = TW_HANDLE referencing a container of type TW_ONEVALUE.

Fill the fields in TW_ONVALUE as follows:

1. ItemType = TWTW_INT32;

2. Item =Bit pattern representing the set of operation that are supported by the Data Source on this capability (TWQC_GET, TWQC_SET, TWQC_GETDEFAULT, TWQC_RESET);


Chapter 7

If the application requests this operation on a capability your Source does not recognize (and you’re sure you’ve implemented all the capabilities that you’re required to), do not disregard the operation, but fill out the TWON_ONEVALUE container with a value of zero(0) for the Item field, indicating no support for any of the DAT CAPABILITY operations, and return a status of TWRC_SUCCESS.



Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_RESET, and MSG_SET


Capability Container: TW_ONEVALUE (in Chapter 8, "Data Types and Data Structures).



DG_CONTROL / DAT_CAPABILITY / MSG_RESET

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_RESET, pCapability);


Valid States

4 only

Description

Change the Current Value of the specified capability back to its power-on value and return the new Current Value.

The power-on value is the Current Value the Source started with when it entered State 4 after a DG_CONTROL / DAT_IDENTITY / MSG_OPENDS. These values are listed as TWAIN defaults (in Chapter 10, "Capabilities”). If “no default” is specified, the Source uses it preferred default value (returned from MSG_GETDEFAULT).

Application




Use MSG_RESET:

• To set the Current Value of the specified capability to the Source’s mandatory or preferred value, and to remove any constants from the allowed values supported by the Source.


Source


If you support the capability, reset the Current Value of the capability back to its power-on value. This value must also match the TWAIN default listed in Chapter 10, "Capabilities.”


Chapter 7

Also return the new Current Value (just like in a MSG_GETCURRENT). Fill in the fields listed below and allocate the container structure and place its handle into pCapability->hContainer. The container should be referenced by a “handle” of type TW_HANDLE.




Set ConType to the container type that matches the type for this capability. Fill the fields in the container structure with the Current Value of the capability (after resetting it as stated above).


Note that this operation is only valid in State 4, unless CAP_EXTENDEDCAPS was negotiated. Any attempt to invoke it in any other state should be disregarded, though the Source should return TWRC_FAILURE with TWCC_SEQERROR.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_CAPUNSUPPORTED /* Capability not supported by source Sources*/ /* 1.6 and newer must use this instead of */ /* using TWCC_BADCAP. */







See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, and MSG_SET

“Capability Constants” on page 8-74.


Listing of all capabilities (in Chapter 10, "Capabilities.”)


Chapter 7

DG_CONTROL / DAT_CAPABILITY / MSG_RESETALL

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPABILITY, MSG_RESETALL, pCapability);


Valid States

4 only

Description

This command resets all of the current values and constraints to their defaults for all of the negotiable capabilities supported by the driver.

Application


pCapability->Cap = CAP_SUPPORTEDCAPSpCapability->ConType = TWON_DONTCARE16pCapability->hContainer = NULL

The Source will not allocate any memory as a part of this call. It will only return a status to indicate success or failure. If this call succeeds then the application must assume that all capabilities have been reset, as well as any DAT structures that are associated with capabilities (such as DAT_IMAGELAYOUT or DAT_JPEGCOMPRESSION).

Source

The TW_CAPABILITY structure has no special meaning for this call. It is not required that the application set the Cap field to CAP_SUPPORTEDCAPS, so do not test for it. Do not change the structure in any way. Do not allocate any memory for this call.

When this call is complete the driver should be restored to factory defaults, matching the settings it had when first installed on the user’s machine.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADCAP /* Unknown capability--Source does not */ /* recognize this capability. This code */ /* should not be used by sources after */ /* 1.6. Applications still need to test */

/* for it for backward compatibility. */


TWCC_CAPUNSUPPORTED /* Capability not supported by */ /* source. Sources 1.6 and newer */ /* must use this instead of */

/* using TWCC_BADCAP. */

TWCC_CAPBADOPERATION /* Operation not supported by */

/* capability. Sources 1.6 and newer */

/* must use this instead of using */

/* TWCC_BADCAP.

TWCC_CAPSEQERROR /* Capability has dependency on other */ /* capability. Sources 1.6 and newer */ /* must use this instead of using */

/* TWCC_BADCAP. */




See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETDEFAULT, MSG_RESET, and MSG_SET

Capability Constants (in Chapter 10, "Capabilities”)


Listing of all capabilities (in Chapter 10, "Capabilities)


Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CAPAB ILITY, MSG_SET, pCapability);


Valid States

4 only (During State 4, applications can also negotiate with Sources for permission to set the value(s) of specific capabilities in States 5 and 6 through CAP_EXTENDEDCAPS.)

Description

Changes the Current Value(s) and Available Values of the specified capability to those specified by the application.

Current Values are set when the container is a TW_ONEVALUE or TW_ARRAY. Available and Current Values are set when the container is a TW_ENUMERATION or TW_RANGE.

Note: Sources are not required to allow restriction of their Available Values, however, this is strongly recommended.

Application

An application will use the setting of a capability’s Current and Available Values differently depending on how the Source was enabled (DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS).

If TW_USERINTERFACE.ShowUI = TRUE

• In State 4, set the Current Value to be displayed to the user as the current value. This value will be used for acquiring the image unless changed by the user or an automatic process (such as ICAP_AUTOBRIGHT).

• In State 4, set the Available Values to restrict the settings displayed to the user and available for use by the Source.

• In State 6, get the Current Value which was chosen by the user or automatic process. This is the setting used in the upcoming transfer.

If TW_USERINTERFACE.ShowUI = FALSE

• In State 4, set the Current Value to the setting that will be used to acquire images (unless automatic settings are set to TRUE, for example: ICAP_AUTOBRIGHT).

• In State 6, get the Current Value which was chosen by any automatic processes. This is the setting used in the upcoming transfer.

If possible, use the same container type in a MSG_SET that the Source returned from a MSG_GET. Allocate the container structure. This is where you will place the value(s) you wish to have the


Source set. Store the handle into pCapability->hContainer. The container must be referenced by a “handle” of type TW_HANDLE.

Set the following:

pCapability->ConType = TWON_ARRAY, TWON_ONEVALUE, TWON_ENUMERATION, or TWON_RANGE

pCapability->Cap = CAP_xxxx designator of capability of interest


Place the value(s) that you wish the Source to use in the container. If successful, these values will supersede any previous negotiations for this capability.

The application must free the container it allocated when the operation is complete and the application no longer needs to maintain the information.

Source

Return TWRC_FAILURE / TWCC_BADCAP:

• If the application requests this operation on a capability your Source does not recognize (and you’re sure you’ve implemented all the capabilities that you’re required to). Disregard the operation.

Return TWRC_FAILURE / TWCC_BADVALUE:

• If the application requests that a value be set that lies outside the supported range of values for the capability (smaller than your minimum value or larger than your maximum value). Set the value to that which most closely approximates the requested value.

• If the application sends a container that you do not support, or do not support in a MSG_SET.

• If the application attempts to set the Available Values and the Source does not support restriction of this capability’s Available Values.

Returns TRCC_CHECKSTATUS:

• If the application requests one or more values that lie within the supported range of values (but that value does not exactly match one of the supported values), set the value to the nearest supported value. The application should then do a MSG_GET to check these values.

Return TWRC_FAILURE / TWCC_SEQERROR:

• If the application sends the MSG_SET outside of State 4 and the capability has not been negotiated in CAP_EXTENDEDCAPS.

If the request is acceptable, use the container structure referenced by pCapability->hContainer to set the Current and Available Values for the capability. If the container type is TWON_ONEVALUE or TWON_ARRAY, set the Current Value for the capability to that value. If the container type is TWON_RANGE or TWON_ENUMERATION, the Source will optionally limit the Available Values for the capability to match those provided by the application, masking all


Chapter 7

other internal values so that the user cannot select them. Though this behavior is not mandatory, it is strongly encouraged.

Important: Sources should accommodate requests to limit Available Values. In the interest of adoptability for the breadth of Source manufacturers, such accommodation is not required. It is recommended, however, that the Sources do so, and that the Source’s user interface be modified (from its power-on state, and when the user interface is raised) to reflect any limitation of choices implied by the newly negotiated settings.

Note: For example, if an application can only accept black and white image data, it tells the Source of this limitation by doing a MSG_SET on ICAP_PIXELTYPE with a TW_ENUMERATION or TW_RANGE container containing only TWPT_BW (black and white).

Note: If the Source disregards this negotiated value and fails to modify its user interface, the user may select to acquire a color image. Either the user’s selection would fail (for reasons unclear to the user) or the transfer would fail (also for unclear reasons for the user). The Source should strive to prevent such situations.

Return Codes

TWRC_SUCCESS

TWRC_CHECKSTATUS /* capability value(s) could not be */ /* matched exactly */

TWRC_FAILURE


TWCC_CAPUNSUPPORTED /* Capability not supported by source. */ /* Sources 1.6 and newer must use this */ /* instead of using TWCC_BADCAP. */

TWCC_CAPBADOPERATION /* Operation not supported by capability. */ /* Sources 1.6 and newer must use this */ /* instead of using TWCC_BADCAP.



TWCC_BADVALUE /* illegal value(s)--outside */ /* Source's range for capability */

TWCC_SEQERROR /* Operation invoked in invalid */ /* state */


See Also

DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, and MSG_RESET





Chapter 7

DG_CONTROL / DAT_CUSTOMDSDATA / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CUSTOMDSDATA,MSG_GET, pCustomData

);

pCustomData = A pointer to a TW_CUSTOMDSDATA structure.

Valid States

4 only

Description

This operation is used by the application to query the data source for its current settings, e.g. DPI, paper size, color format. The sources settings will be returned in a TW_CUSTOMDSDATA structure. The actual format of the data in this structure is data source dependent and not defined by TWAIN.

Application

pDest references the sources identity structure. pCustomData points to a TW_CUSTOMDSDATA structure.

Source

Fills the pCustomData pointer with source specific settings. If supported, CAP_ENABLEDSUIONLY and CAP_CUSTOMDSDATA are required.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_SEQERROR

See Also

Capability CAP_CUSTOMDSDATA


DG_CONTROL / DAT_CUSTOMDSDATA / MSG_SET

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_CUSTOMDSDATA,MSG_SET, pCustomData);

pCustomData = A pointer to a TW_CUSTOMDSDATA structure.

Valid States

4 only

Description

This operation is used by the application to set the current settings for a data source to a previous state as defined by the data contained in the pCustomData data structure. The actual format of the data in this structure is data source dependent and not defined by TWAIN.

Application

pDest references the sources identity structure. pCustomData points to a TW_CUSTOMDSDATA structure.

Source

Changes its current settings to the values specified in the pCustomData structure.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_SEQERROR

See Also

Capability CAP_CUSTOMDSDATA


Chapter 7

DG_CONTROL / DAT_DEVICEEVENT / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_DEVICEEVENT, MSG_GET, pSourceDeviceEvent);

pSourceDeviceEvent = A pointer to a TW_DEVICEEVENT structure

Valid States

4 through 7

Description

Upon receiving a DG_CONTROL / DAT_NULL / MSG_DEVICEEVENT from the Source, the Application must immediately make this call to obtain the event information.

Sources must queue the data for each event so that it is available for this call.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL Capability not supported.

TWCC_SEQERROR No events in the queue, or not in States 4 through 7.

See Also

DG_CONTROL / DAT_NULL / MSG_DEVICEEVENTCAP_DEVICEEVENT


DG_CONTROL / DAT_ENTRYPOINT / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_ENTRYPPINT, MSG_GET, pEntryPoint);

pEntryPoint = A pointer to a TW_ENTRYPOINT structure

Valid States

3

Description

A TWAIN 2.0 Application examines the Source’s TW_IDENTITY .SupportedGroups. If DF_DSM2 is set, then it must issue this call to get the entry points for the Source Manager. If the conditions are not met then the Source Manager will return TWRC_FAILURE / TWCC_BADPROTOCOL, and the Application must assume TWAIN 1.x behavior.

The Application gets five entry points in the TW_ENTRYPOINT structure:

* the DSM_Entry function, this may be ignored * the DSM_MemAllocate function, used by the Application to allocate memory that will be freed by the Source * the DSM_MemFree function, used by the Application to free memory allocated by the Source * the DSM_MemLock function, used by the Application to get a usable pointer from a handle it got from the Source. * the DSM_MemUnlock function, used when the Application is done with the memory it got from the Source. This call is usually made just before DSM_MemFree.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL

TWCC_SEQERROR

See Also

Identifying TWAIN 2.0 Elements, in Chapter 2, "Technical Overview.”


Chapter 7

DG_CONTROL / DAT_ENTRYPOINT / MSG_SET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_ENTRYPOINT, MSG_SET, pEntryPoint);

pEntryPoint = A pointer to a TW_ENTRYPOINT structure

Valid States

The TWAIN 2.0 Source Manager issues this command to Sources (that set DF_DS2) prior of any other command sent by the Application. In most cases it will immediately precede the call to DG_CONTROL / DAT_IDENTITY / MSG_OPEN.

The Source gets five entry points in the TW_ENTRYPOINT structure:

• the pointer to the DSM_Entry function, used for any DAT_NULL operations such as DG_CONTROL / DAT_NULL / MSG_XFERREADY.

• the DSM_MemAllocate function, used by the Source to allocate memory that will be freed by the Application

• the DSM_MemFree function, used by the Source to free memory allocated by the Application

• *the DSM_MemLock function, used by the Source to get a usable pointer from a handle it got from the Application.

• the DSM_MemUnlock function, used when the Source is done with the memory it got from the Application. This call is usually made just before DSM_MemFree.

Note: TWAIN 1.x Sources must continue to find and load the Source Manager DSM_Entry on their own.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL

TWCC_SEQERROR

See Also

Identifying TWAIN 2.0 Elements, in Chapter 2, "Technical Overview.”


DG_CONTROL/ DAT_EVENT / MSG_PROCESSEVENT

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_EVENT, MSG_PROCESSEVENT, pEvent);

pEvent = A pointer to a TW_EVENT structure.

Valid States

5 through 7

Description

This operation supports the distribution of events from the application to Sources so that the Source can maintain its user interface and return messages to the application. Once the application has enabled the Source, it must immediately begin sending to the Source all events that enter the application’s main event loop. This allows the Source to update its user interface in real-time and to return messages to the application which cause state transitions. Even if the application overrides the Source’s user interface, it must forward all events once the Source has been enabled. The Source will tell the application whether or not each event belongs to the Source.

Note: Events only need to be forwarded to the Source while it is enabled.

The Source should be structured such that identification of the event’s “owner” is handled before doing anything else. Further, the Source should return immediately if the Source isn’t the owner. This convention should minimize performance concerns for the application (remember, these events are only sent while a Source is enabled—that is, just before and just after the transfer is taking place).

Application

On Windows: Make pEvent->pEvent point to the message structure.

On Macintosh: SeeChapter 3, "Application Implementation.”

Note: On return, the application should check the Return Code from DSM_Entry() for TWRC_DSEVENT or TWRC_NOTDSEVENT. If TWRC_DSEVENT is returned, the application should not process the event—it was consumed by the Source. If TWRC_NOTDSEVENT is returned, the application should process the event as it normally would.

With either of these Return Codes, the application should also check the pEvent->TWMessage and switch on the result. This is the mechanism used by the Source to notify the application that a data transfer is ready or that it should close the Source. The Source can return one of the following messages:

MSG_XFERREADY /* Source has one or more images */ /* ready to transfer */


Chapter 7

MSG_CLOSEDSREQ /* Source wants to be closed, */ /* usually initiated by a */ /* user-generated event */

MSG_NULL /* no message for application */

Source

Process this operation immediately and return to the application immediately if the event doesn’t belong to you. Be aware that the application will be sending thousands of messages to you. Consider in-line processing and global flags to speed implementation.

Return Codes

TWRC_DSEVENT /* Source consumed event--application */ /* should not process it */

TWRC_NOTDSEVENT /* Event belongs to application - */ /* process as usual */

TWRC_FAILURE

TWCC_BADDEST /* No such Source in-session */ /* with application */


See Also

DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQDG_CONTROL / DAT_NULL / MSG_XFERREADY

Event loop information (in Chapter 7, "Operation Triplets.”)


DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORY

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_AUTOMATICCAPTUREDIRECTORY, pSourceFileSystem);

pSourceFileSystem = A pointer to a TW_FILESYSTEM structure

Valid States

4 only

Description

This operation selects the destination directory within the Source (camera, storage, etc), where images captured using CAP_AUTOMATICCAPTURE will be stored. This command only selects the destination directory (a file of type TWFT_DIRECTORY). The directory must exist and be accessible to the Source. The creation of images within the directory is at the discretion of the Source, and may result in the creation of additional sub-directories.

In all other regards the behavior of this operation is the same as DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY.

If the application does not specify a directory for automatic capture, then the destination of the images is left to the discretion of the Source. A directory named /Images is recommended, but not required.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL - capability not supported.

TWCC_DENIED - operation denied (device not ready).

TWCC_FILENOTFOUND - specified InputName does not exist.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_COPYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIADG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSEDG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAMECAP_AUTOMATICCAPTURE


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_CHANGEDIRECTORY, pSourceFileSystem);


Valid States

4 only

Description

This operation selects the current device within the Source (camera, storage, etc). If the device is a TWFT_DOMAIN, then this command enters a directory that can contain TWFT_HOST files. If the device is a TWFT_HOST, then this command enters a directory that can contain TWFT_DIRECTORY files. If the device is a TWFT_DIRECTORY, then this command enters a directory that can contain TWFT_DIRECTORY or TWFT_IMAGE files.

Sources can support part or all of the storage hierarchy that is one of the following:

/Domain/Host/Directory/

/Host/Directory/…

/Directory/…

(Storage not supported)

It is permitted to mix domain, host, and directory names in the root file system of the Source. To help resolve any potential name conflict, Applications should set TW_FILESYSTEM-> FileType to the appropriate value for the topmost file. If this is not done and there is a name conflict, the Source’s default behavior must be to use the file of type TWFT_DIRECTORY or TWFT_HOST, in that order.

For example, consider two files named “abc” in the root of a Source:

/abc/123 (abc is a domain)

/abc/789 (abc is a directory)

Change directory to the first one by setting FileType to TWFT_DOMAIN, or to the second one by setting FileType to TWFT_DIRECTORY. The FileType for each will be discovered while browsing the directory using DAT_GETFILEFIRST and DAT_GETFILENEXT. If the FileType is not specified, then the Source must change to the “/abc/789” directory.

Example:

A Source supports two devices: /Camera and /Disk. If an application changes directory to /Camera, then it can negotiate imaging parameters and transfer images in a traditional fashion. If an application changes directory to /Disk/abc/xyz, then it cannot negotiate imaging


parameters (the images have already been captured); all it can do is browse the directory tree and transfer the images it finds.

The Application sets the new current working directory by placing in the InputName field an absolute or relative path. The Source returns the absolute path and name of the new directory in the OutputName field. The special filename dot “.” can be used to retrieve the name of the current directory. The special filename dot-dot “..” can be used to change to the parent directory. Refer to the section on File Systems for more information.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - operation denied (device not ready).

TWCC_FILENOTFOUND - specified InputName does not exist.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_COPYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_COPY

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_COPY, pSourceFileSystem);


Valid States

4 only

Description

This operation copies a file or directory. Absolute and relative pathnames are supported. A file may not be overwritten with this command. If an Application wishes to do this, it must first delete the unwanted file and then reissue the Copy command.

The Application specifies the path and name of the entry to be copied in InputName. The Application specifies the new patch and name in OutputName.

It is not permitted to copy files into the root directory.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - file cannot be deleted (root file, or protected by Source).

TWCC_FILEEXISTS - specified OutputName already exists.

TWCC_FILENOTFOUND - InputName not found or OutputName invalid.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


DG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORY

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_CREATEDIRECTORY, pSourceFileSystem);


Valid States

4 only

Description

This operation creates a new directory within the current directory. Pathnames are not allowed, only the name of the new directory can be specified.

Example:

“abc” is valid.“/Disk/abc” is not valid.

The Application specifies the name of the new directory in InputName.

On success, the Source returns the absolute path and name of the new directory in OutputName.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - cannot create directory in current directory, directories may not be created in root, or the Source may opt to prevent the creation of new directories in some instances, for instance if the new directory would be too deep in the tree.

TWCC_FILEEXISTS - the specified InputName already exists.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_COPYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


DG_CONTROL / DAT_FILESYSTEM / MSG_DELETE

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_DELETE, pSourceFileSystem);


Valid States

4 only

Description

This operation deletes a file or directory on the device. Pathnames are not allowed, only the name of the file or directory to be deleted can be specified. Recursive deletion can be specified by setting the pSourceFileSystem->Recursive to TRUE.

Example:

“abc” is valid.“/Disk/abc” is not valid.

The Application specifies the name of the entry to be deleted in InputName. There is no return in OutputName on success.

The Application cannot delete entries in the root directory. The Application cannot delete directories unless they are empty.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



TWCC_FILENOTFOUND - filename not found.

TWCC_NOTEMPTY - directory is not empty, and cannot be deleted.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILE


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


DG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_FORMATMEDIA, pSourceFileSystem);


Valid States

4 only

Description

This operation formats the specified storage. This operation destroys all images and sub-directories under the selected device. Use with caution.

The Application specifies the name of the device to be deleted in InputName. There is no data returned by this call.

The Application cannot format the root directory. Sources may opt to protect their media from this command, so Applications must check return and condition codes.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - format denied (root directory, or protected by Source).

TWCC_FILENOTFOUND - filename not found.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_GETCLOSE, pSourceFileSystem);


Valid States

4 through 6

Description

The operation frees the Context field in pSourceFileSystem.

Every call to DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILE must be matched by a call to MSG_GETCLOSE to release the Context field in the pSourceFileSystem structure.

An Application may (erroneously) issue this operation at any time (even if a MSG_GETFIRSTFILE has not been issued yet). Sources must protect themselves from such uses. See the section on File Systems for more information on why and how this must be done.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_SEQERROR - not state 4, 5 or 6.

See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILE

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_GETFIRSTFILE, pSourceFileSystem);


Valid States

4 through 6

Description

This operation gets the first filename in a directory, and returns information about that file (the same information that can be retrieved with MSG_GETINFO).

The Source positions the Context to point to the first filename. InputName is ignored. OutputName contains the absolute path and name of the file. If the Application enables the Source at this time, and the PendingXfers.Count is non-zero, the Application will immediately receive a MSG_XFERREADY, and the current image will be transferred.

Applications must not assume any ordering of the files delivered by the Source, with one exception: if MSG_GETFIRSTFILE is issued in the root directory, then the operation must return a TWFT_CAMERA device.

NB: “.” and “..” are NEVER reported by this command.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - file exists, but information about it has not been returned.

TWCC_FILENOTFOUND - directory is empty.

TWCC_SEQERROR - not state 4, 5 or 6.

See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFO


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFO

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_GETINFO, pSourceFileSystem);


Valid States

4 through 7

Description

This operation fills the information fields in pSourceFileSystem.

InputName contains the absolute or relative path and filename of the requested file. OutputName returns the absolute path to the file.

Example InputName:

“abc” is valid.“/Disk/abc” is valid.The empty string ““ returns information about the current file (if any).“.” returns information about the current directory.“..” returns information about the parent directory.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - - file exists, but information about it has not been returned.

TWCC_FILENOTFOUND - specified file does not exist.

TWCC_SEQERROR - not state 4 - 7, or no current file.

See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILE

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_GETNEXTFILE, pSourceFileSystem);


Valid States

4 through 6

Description

This operation gets the next filename in a directory, and returns information about that file (the same information that can be retrieved with MSG_GETINFO).

The Source positions the Context to point to the next filename. InputName is ignored. OutputName contains the absolute path and name of the file. If the Application enables the Source at this time, and the PendingXfers.Count is non-zero, the Application will immediately receive a MSG_XFERREADY, and the current image will be transferred.

A call to MSG_GETFIRSTFILE must be issued on a given directory before the first call to MSG_GETNEXTFILE.

NB: The “.” and “..” entries are NEVER reported by this command

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_DENIED - file exists, but information about it has not been returned.

TWCC_FILENOTFOUND - directory is empty.

TWCC_SEQERROR - not state 4, 5 or 6, or invalid context (must issue

MSG_GETFILEFIRST before calling MSG_GETNEXTFILE).

See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILE


DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_RENAME


Chapter 7

DG_CONTROL / DAT_FILESYSTEM / MSG_RENAME

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_FILESYSTEM, MSG_RENAME, pSourceFileSystem);


Valid States

4 only

Description

This operation renames (and optionally moves) a file or directory. Absolute and relative path names are supported. A file may not be overwritten with this command. If an Application wishes to do this it must first delete the unwanted file, then issue the rename command.

The Application specifies the path and name of the entry to be renamed in InputName. The Application specifies the new path and name in OutputName.

Filenames in the root directory cannot be moved or renamed.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



TWCC_FILEEXISTS - specified OutputName already exists.

TWCC_FILENOTFOUND - InputName not found or OutputName invalid.


See Also

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIA DG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSE DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILE


DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDS(from Application to Source Manager)

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_CLOSEDS, pSourceIdentity);

pSourceIdentity = A pointer to a TW_IDENTITY structure.

Valid States

4 only (Transitions to State 3, if successful)

Description

When an application is finished with a Source, it must formally close the session between them using this operation. This is necessary in case the Source only supports connection with a single application (many desktop scanners will behave this way). A Source such as this cannot be accessed by other applications until its current session is terminated.

Application

Reference pSourceIdentity to the application’s copy of the TW_IDENTITY structure for the Source whose session is to be ended. The application needs to unload the Source from memory after it is closed. The process for unloading the Source is similar to that used to unload the Source Manager.

Source Manager

On Macintosh only—Closes the Source and removes it from memory, following receipt of TWRC_SUCCESS from the Source.

On Windows only—Checks its internal counter to see whether any other applications are accessing the specified Source. If so, the Source Manager takes no other action. If the closing application is the last to be accessing this Source, the Source Manager closes the Source (forwards this triplet to it) and removes it from memory, following receipt of TWRC_SUCCESS from the Source.

Upon receiving the request from the Source Manager, the Source immediately prepares to terminate execution.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


See Also



Chapter 7

DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDS(from Source Manager to Source)

Call

DS_Entry(pOrigin, DG_CONTROL, DAT_IDENTITY, MSG_CLOSEDS, pSourceIdentity);


Valid States

4 only (Transitions Source back to the “loaded but not open” State - approximately State 3.5)

Description

Closes the Source so it can be unloaded from memory. The Source responds by doing its shutdown and clean-up activities needed to ensure the heap will be “clean” after the Source is unloaded. Under Windows, the Source will only be unloaded if the connection with the last application accessing it is about to be broken. The Source will know this by its internal “connect count” that should be maintained by any Source that supports multiple application connects.

Source Manager

pSourceIdentity is filled from a previous MSG_OPENDS operation.

Source

Perform all necessary housekeeping in anticipation of being unloaded. Be sure to dispose of any memory buffers that the Source has allocated locally, or that may have become the Source’s responsibility during the course of the TWAIN session. The Source exists in a shared memory environment. It is therefore critical that all remnants of the Source, except the entry point (initial) code, be removed as the Source prepares to be unloaded.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_OPERATIONERROR /* Internal Source error; */ /* handled by the Source */

See Also



DG_CONTROL / DAT_IDENTITY / MSG_GET(from Source Manager to Source)

Call

DS_Entry(pOrigin, DG_CONTROL, DAT_IDENTITY, MSG_GET, pSourceIdentity);


Valid States

3 through 7 (Yes, the Source must be able to return the identity before it is opened.)

Description

This operation triplet is generated only by the Source Manager and is sent to the Source. It returns the identity structure for the Source.

Source Manager

No special set up or action required.

Source

Fills in all fields of pSourceIdentity except the Id field which is only modified by the Source Manager. This structure was allocated by either the application or the Source Manager depending on which one initiated the MSG_OPENDS operation for the Source.

Note: Sources should locate the code that handles initialization of the Source (responding to MSG_OPENDS) and identification (DAT_IDENTITY / MSG_GET) in the segment first loaded when the DLL/code resource is invoked. Responding to the identification operation should not cause any other segments to be loaded. Code to handle all other operations and to support the user interface should be located in code segments that will be loaded upon demand. Remember, the Source is a “guest” of the application and needs to be sensitive to use of available memory and other system resources. The Source Manager’s perceived performance may be adversely affected unless the Source efficiently handles identification requests.

Return Codes

TWRC_SUCCESS /* This operation must succeed. */


Chapter 7

DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULT

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_GETDEFAULT, pSourceIdentity);


Valid States

3 through 7

Description

Gets the identification information of the system default Source.

Application


Source Manager

Fills the structure pointed to by pSourceIdentity with identifying information about the system default Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_NODS /* no Sources found matching */ /* application's SupportedGroups */

TWCC_LOWMEMORY /* not enough memory to perform */ /* this operation */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_GETFIRSTDG_CONTROL / DAT_IDENTITY / MSG_GETNEXTDG_CONTROL / DAT_IDENTITY / MSG_OPENDSDG_CONTROL / DAT_IDENTITY / MSG_USERSELECT


DG_CONTROL / DAT_IDENTITY / MSG_GETFIRST

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_GETFIRST, pSourceIdentity);


Valid States

3 through 7

Description

The application may obtain a list of all Sources that are currently available on the system which match the application’s supported groups (DGs, that the application specified in the SupportedGroups field of its TW_IDENTITY structure). To obtain the complete list of all available Sources requires invocation of a series of operations. The first operation uses MSG_GETFIRST to find the first Source on “the list” (whichever Source the Source Manager finds first). All the following operations use DG_CONTROL / DAT_IDENTITY / MSG_GETNEXT to get the identity information, one at a time, of all remaining Sources.

Note: The application must invoke the MSG_GETFIRST operation before a MSG_GETNEXT operation. If the MSG_GETNEXT is invoked first, the Source Manager will fail the operation (TWRC_ENDOFLIST).

If the application wants to cause a specific Source to be opened, one whose ProductName the application knows, it must first establish the existence of the Source using the MSG_GETFIRST/MSG_GETNEXT operations. Once the application has verified that the Source is available, it can request that the Source Manager open the Source using DG_CONTROL / DAT_IDENTITY / MSG_OPENDS. The application must not execute this operation without first verifying the existence of the Source because the results may be unpredictable.

Application


Source Manager

Fills the TW_IDENTITY structure pointed to by pSourceIdentity with the identity information of the first Source found by the Source Manager within the TWAIN directory/folder.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_NODS /* No Sources can be found */


Chapter 7

TWCC_LOWMEMORY /* Not enough memory to perform */ /* this operation */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULTDG_CONTROL / DAT_IDENTITY / MSG_GETNEXTDG_CONTROL / DAT_IDENTITY / MSG_OPENDSDG_CONTROL / DAT_IDENTITY / MSG_USERSELECT


DG_CONTROL / DAT_IDENTITY / MSG_GETNEXT

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_GETNEXT, pSourceIdentity);


Valid States

3 through 7

Description

The application may obtain a list of all Sources that are currently available on the system which match the application’s supported groups (DGs, that the application specified in the SupportedGroups field of its TW_IDENTITY structure). To obtain the complete list of all available Sources requires invocation of a series of operations. The first operation uses DG_CONTROL / DAT_IDENTITY / MSG_GETFIRST to find the first Source on “the list” (whichever Source the Source Manager finds first). All the following operations use MSG_GETNEXT to get the identity information, one at a time, of all remaining Sources.

Note: The application must invoke the MSG_GETFIRST operation before a MSG_GETNEXT operation. If the MSG_GETNEXT is invoked first, the Source Manager will fail the operation (TWRC_ENDOFLIST).

If the application wants to cause a specific Source to be opened, one whose ProductName the application knows, it must first establish the existence of the Source using the MSG_GETFIRST/MSG_GETNEXT operations. Once the application has verified that the Source is available, it can request that the Source Manager open the Source using DG_CONTROL / DAT_IDENTITY / MSG_OPENDS. The application must not execute this operation without first verifying the existence of the Source because the results may be unpredictable.

Application


Source Manager

Fills the TW_IDENTITY structure pointed to by pSourceIdentity with the identity information of the next Source found by the Source Manager within the TWAIN directory/folder.

Return Codes

TWRC_SUCCESS

TWRC_ENDOFLIST /* after MSG_GETNEXT if no more */ /* Sources */

TWRC_FAILURE


Chapter 7


See Also

DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULTDG_CONTROL / DAT_IDENTITY / MSG_GETFIRSTDG_CONTROL / DAT_IDENTITY / MSG_OPENDSDG_CONTROL / DAT_IDENTITY / MSG_USERSELECT


DG_CONTROL / DAT_IDENTITY / MSG_OPENDS(from Application to Source Manager)

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_OPENDS, pSourceIdentity);


Valid States


Description

Loads the specified Source into main memory and causes its initialization.

Application

The application may specify any available Source’s TW_IDENTITY structure in pSourceIdentity. That structure may have been obtained using a MSG_GETFIRST, MSG_GETNEXT, or MSG_USERSELECT operation. If the session with the Source Manager was closed since the identity structure being used was obtained, the application must set the Id field to 0. This will cause the Source Manager to issue the Source a new Id. The application can have the Source Manager open the default Source by setting the ProductName field to “\0” (Null string) and the Id field to zero.

Source Manager

Opens the Source specified by pSourceIdentity and creates a unique Id value for this Source (under Microsoft Windows, this assumes that the Source hadn’t already been opened by another application). This value is recorded in pSourceIdentity->Id. The Source Manager passes the triplet on to the Source to have the remaining fields in pSourceIdentity filled in.

Upon receiving the request from the Source Manager, the Source fills in all the fields in pSourceIdentity except for Id. If an application tries to connect to a Source that is already connected to its maximum number of applications, the Source returns TWRC_FAILURE/TWCC_MAXCONNECTIONS.

Warning: The Source and application must not assume that the value written into pSourceIdentity.Id will remain constant between sessions. This value is used internally by the Source Manager to uniquely identify applications and Sources and to manage the connections between them. During a different session, this value may still be valid but might be assigned to a different application or Source! Don’t use this value directly.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


Chapter 7

TWCC_LOWMEMORY /* not enough memory to */ /* open the Source */

TWCC_MAXCONNECTIONS /* Source cannot support*/ /* another connection */

TWCC_NODS /* specified Source was */ /* not found */

TWCC_OPERATIONERROR /* internal Source error;*/ /* handled by the Source */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDSDG_CONTROL / DAT_IDENTITY / MSG_GETDG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULTDG_CONTROL / DAT_IDENTITY / MSG_GETFIRSTDG_CONTROL / DAT_IDENTITY / MSG_GETNEXT DG_CONTROL / DAT_IDENTITY / MSG_USERSELECT


DG_CONTROL / DAT_IDENTITY / MSG_OPENDS(from Source Manager to Source)

Call

DS_Entry(pOrigin, DG_CONTROL, DAT_IDENTITY, MSG_OPENDS, pSourceIdentity);


Valid States

Source is loaded but not yet open (approximately State 3.5, session transitions to State 4, if successful).

Description

Opens the Source for operation.

Source Manager

pSourceIdentity is filled in from a previous DG_CONTROL / DAT_IDENTITY / MSG_GET and the Id field should be filled in by the Source Manager.

Source

Initializes any needed internal structures, performs necessary checks, and loads all resources needed for normal operation.

Windows only: Source should record a copy of *pOrigin, the application’s TW_IDENTITY structure, whose Id field maintains a unique number identifying the application that is calling. Sources that support only a single connection should examine pOrigin->Id for each operation to verify they are being called by the application they acknowledge being connected with. All requests from other applications should fail (TWRC_FAILURE / TWCC_MAXCONNECTIONS). The Source is responsible for managing this, not the Source Manager (the Source Manager does not know in advance how many connections the Source will support).

Macintosh Note: Since the Source(s) and the Source Manager connected to a particular application live within that application’s heap space, and are not shared with any other application, the discussion about multiply-connected Sources and verifying which application is invoking an operation is not relevant. A Source or Source Manager on the Macintosh can only be connected to a single application, though multiple copies of a Source or the Source Manager may be active on the same host simultaneously. These instances simply exist in different applications’ heaps. If the instances need to communicate with one another, they might use a special file, Gestalt selector, or other IPC mechanism.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


Chapter 7

TWCC_LOWMEMORY /* not enough memory to */ /* open the Source */

TWCC_MAXCONNECTIONS /* Source cannot support */ /* another connection */

TWCC_OPERATIONERROR /* internal Source error;*/ /* handled by the Source */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_CLOSEDSDG_CONTROL / DAT_IDENTITY / MSG_GET


DG_CONTROL / DAT_IDENTITY / MSG_SET

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_SET, pTwIdentity);

_pTwIdentity = A pointer to a TW_IDENTITY structure containing a valid TW_IDENTITY for a Data source.

Valid States

3

Description

This operation triplet is generated by the application and is consumed by the Data Source Manager. It allows an application to set the default TWAIN driver, which is reported back by DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULT.

Application

The application must specify an available Source’s TW_IDENTITY structure in pTwIdentity. That structure must have been obtained using a MSG_GETFIRST, MSG_GETNEXT, or MSG_USERSELECT operation since the Source Manager was last opened.

Source Manager

Sets a new default TWAIN driver.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADVALUE /* Invalid DS in TW_IDENTITY */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULT


Chapter 7


Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_IDENTITY, MSG_USERSELECT, pSourceIdentity);


Valid States

3 through 7

Description

This operation should be invoked when the user chooses Select Source... from the application’s File menu (or an equivalent user action). This operation causes the Source Manager to display the Select Source dialog. This dialog allows the user to pick which Source will be used during subsequent Acquire operations. The Source selected becomes the system default Source. This default persists until a different Source is selected by the user. The system default Source may be overridden by an application (the override is local to only that application). Only Sources that can supply data matching one or more of the application’s SupportedGroups (from the application’s identity structure) will be selectable. All others will be unavailable for selection.

Application

If the application wants a particular Source, other than the system default, to be highlighted in the Select Source dialog, it should set the ProductName field of the structure pointed to by pSourceIdentity to the ProductName of that Source. This information should have been obtained from an earlier operation using DG_CONTROL / DAT_IDENTITY / MSG_GETFIRST, MSG_GETNEXT, or MSG_USERSELECT. Otherwise, the application should set the ProductName field in pSourceIdentity to the null string (“\0”). In either case, the application should set the Id field in pSourceIdentity to zero.

If the Source Manager can’t find a Source whose ProductName matches that specified by the application, it will select the system default Source (the default that matches the SupportedGroups of the application). This is not considered to be an error condition. No error will be reported. The application should check the ProductName field of pSourceIdentity following this operation to verify that the Source it wanted was opened.

Source Manager

The Source Manager displays the Select Source dialog and allows the user to select a Source. When the user clicks the “OK” button (“Select” button in the Microsoft Windows Source Manager) in the Select Source dialog, the system default Source (maintained by the Source Manager) will be changed to the selected Source. This Source’s identifying information will be written into pSourceIdentity.

The “Select” button (“OK” button in the Macintosh Source Manager) will be grayed out if there are no Sources available matching the SupportedGroups specified in the application’s identity structure, pOrigin. The user must click the “Cancel” button to exit the Select Source dialog. The application cannot discern from this Return Code whether the user simply canceled the


selection or there were no Sources for the user to select. If the application really wants to know whether any Sources are available that match the specified SupportedGroups it can invoke a MSG_GETFIRST operation and check for a successful result.

It copies the TW_IDENTITY structure of the selected Source into pSourceIdentity.

Suggestion for Source Developers: The string written in the Source’s TW_IDENTITY.ProductName field should clearly and unambiguously identify your product or the Source to the user (if the Source can be used to control more than one device). ProductName contains the string that will be placed in the Select Source dialog (accompanied, on the Macintosh, with an icon from the Source’s resource file representing the Source). It is further suggested that the Source’s disk file name approximate the ProductName to assist the user in equating the two.

Return Codes

TWRC_SUCCESS

TWRC_CANCEL /* User clicked cancel button - maybe there */ /* were no Sources */

TWRC_FAILURE

TWCC_LOWMEMORY /* not enough memory to perform this */ /* operation */

See Also

DG_CONTROL / DAT_IDENTITY / MSG_GETDEFAULTDG_CONTROL / DAT_IDENTITY / MSG_GETFIRSTDG_CONTROL / DAT_IDENTITY / MSG_GETNEXTDG_CONTROL / DAT_IDENTITY / MSG_OPENDS


Chapter 7

DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQ(from Source to Application - Windows only)

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_NULL, MSG_CLOSEDSREQ, NULL);

This operation requires no data (NULL).

Valid States

5 through 7 (This operation causes the session to transition to State 5.)

Description

While the Source is enabled, the application is sending all events/messages to the Source. The Source will use one of these events/messages to indicate to the application that it needs to be closed.

On Windows, the Source sends this DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQ to the Source Manager to cause the Source Manager to post a private message to the application’s event/message loop. This guarantees that the application will have an event/message to pass to the Source Manager so it will be able to communicate the Source’s Close request back to the application.

On Macintosh, refer to Chapter 3, "Application Implementation.”

Source (on Windows only)

Source creates this triplet with NULL data and sends it to the Source Manager via the Source Manager’s DSM_Entry point.

pDest is the TW_IDENTITY structure of the application.

Source Manager (on Windows only)

Upon receiving this triplet, the Source Manager posts a private message to the application’s event/message loop. Since the application is forwarding all events/messages to the Source while the Source is enabled, this creates a communication device needed by the Source. When this private message is received by the Source Manager (via the DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT operation), the Source Manager will insert a MSG_CLOSEDSREQ into the TWMessage field on behalf of the Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_BADDEST /* No such application in session with*/ /* Source */


See Also

DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENTDG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS


Chapter 7

DG_CONTROL / DAT_NULL / MSG_DEVICEEVENT(from Source to Application)

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_NULL, MSG_DEVICEEVENT, NULL);

This operation requires no data (NULL)

Valid States

4 through 7

Description

When enabled the source sends this message to the Application to alert it that some event has taken place. Upon receiving this message, the Application must immediately issue a call to DG_CONTROL / DAT_DEVICEEVENT / MSG_GET to obtain the event information.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_SEQERROR - operation invoked in invalid state.

TWCC_BADDEST - no such application in session with Source.

See Also


Capability - CAP_DEVICEEVENT


DG_CONTROL / DAT_NULL / MSG_XFERREADY(from Source to Application - applies to Windows only)

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_NULL, MSG_XFERREADY, NULL);

This operation requires no data (NULL).

Valid States

5 only (This operation causes the transition to State 6.)

Description

While the Source is enabled, the application is sending all events/messages to the Source. The Source will use one of these events/ messages to indicate to the application that the data is ready to be transferred.

On Windows, the Source sends this DG_CONTROL / DAT_NULL / MSG_XFERREADY to the Source Manager to cause the Source Manager to post a private message to the application’s event/message loop. This guarantees that the application will have an event/message to pass to the Source and the Source will be able to communicate its “transfer ready” announcement back to the application.

On Macintosh, refer to Chapter 3, "Application Implementation.”

Source (on Windows only)

Source creates this triplet with NULL data and sends it to the Source Manager via the Source Manager’s DSM_Entry point.

pDest is the TW_IDENTITY structure of the application.

Source Manager

Upon receiving this triplet, the Source Manager posts a private message to the application’s event/message loop. Since the application is forwarding all events/messages to the Source while the Source is enabled, this creates a communication device needed by the Source. When this private message is received by the Source Manager (via the DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT operation), the Source Manager will insert the MSG_XFERREADY into the TWMessage field on behalf of the Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_BADDEST /* No such application in session with*/ /* Source */


Chapter 7

See Also

DG_CONTROL / DAT_EVENT / MSG_PROCESSEVENTDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMXFER / MSG_GETDG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET



Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_PARENT, MSG_CLOSEDSM, pParent);

On Windows - pParent = points to the window handle (hWnd) that will act as the Source’s “parent”. The variable is of type TW_INT32 and the low word of this variable must contain the window handle.

On Macintosh - pParent = should be a 32-bit NULL value.

Valid States

3 only (causes transition back to State 2, if successful)

Description

When the application has closed all the Sources it had previously opened, and is finished with the Source Manager (the application plans to initiate no other TWAIN sessions), it must close the Source Manager. The application should unload the Source Manager DLL or code resource after the Source Manager is closed—unless the application has immediate plans to use the Source Manager again.

Application

References the same pParent parameter that was used during the “open Source Manager” operation. If the operation returns TWRC_SUCCESS, the application should unload the Source Manager from memory.

Source Manager

Does any housekeeping needed to prepare for being unloaded from memory. This housekeeping is transparent to the application.

Windows only—If the Source Manager is open to at least one other application, it will clean up just activities relative to the closing application, then return TWRC_SUCCESS. The application will attempt to unload the Source Manager DLL. Windows will tell the application that the unload was successful, but the Source Manager will remain active and connected to the other application(s).

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


See Also



Chapter 7


Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_PARENT, MSG_OPENDSM, pParent);

On Windows - pParent = points to the window handle (hWnd) that will act as the Source’s “parent”. The variable is of type TW_INT32 and the low word of this variable must contain the window handle.

On Macintosh - pParent = should be a 32-bit NULL value.

Valid States

2 only (causes transition to State 3, if successful)

Description

Causes the Source Manager to initialize itself. This operation must be executed before any other operations will be accepted by the Source Manager.

Application

Windows only—The application should set the pParent parameter to point to a window handle (hWnd) of an open window that will remain open until the Source Manager is closed. If application can’t open the Source Manager DLL, Windows displays an error box (this error box can be disabled by a prior call to SetErrorMode (SET_NOOPENFILEERRORBOX)).

Macintosh only—Set pParent to NULL.

Source Manager

Initializes and prepares itself for subsequent operations. Maintains a copy of pParent.

Windows only—If Source Manager is already open, Source Manager won’t reinitialize but will retain a copy of pParent.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also




Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_PASSTHRU,MSG_PASSTHRU, pSourcePassthru);

pSourcePassthru = A pointer to a TW_PASSTHRU structure

Valid States

4 through 7

Description

PASSTHRU is intended for the use of Source writers writing diagnostic applications. It allows raw communication with the currently selected device in the Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_SEQERROR - command could not be completed in this state.

See Also

CAP_PASSTHRU


Chapter 7


Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_PENDINGXFERS, MSG_ENDXFER, pPendingXfers);

pPendingXfers = A pointer to a TW_PENDINGXFERS structure

Valid States

6 and 7

When DAT_XFERGROUP is set to DG_IMAGE:

(Transitions to State 5 if this was the last transfer (pPendingXfers->Count == 0). Transitions to State 6 if there are more transfers pending (pPendingXfers->Count != 0). To abort all remaining transfers and transition from State 6 to State 5, use DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET.

When DAT_XFERGROUP is set to DG_AUDIO:

Transitions to State 6 no matter what the value of pPendingXfers->Count.

Description

This triplet is used to cancel or terminate a transfer. Issued in state 6, this triplet cancels the next pending transfer, discards the transfer data, and decrements the pending transfers count. In state 7, this triplet terminates the current transfer. If any data has not been transferred (this is only possible during a memory transfer) that data is discarded.

The application can use this operation to cancel the next pending transfer (Source writers take note of this). For example, after the application checks TW_IMAGEINFO (or TW_AUDIOINFO, if transferring audio snippets), it may decide to not transfer the next image. The operation must be sent prior to the beginning of the transfer, otherwise the Source will simply abort the current transfer. The Source decrements the number of pending transfers.

Application

The application must invoke this operation at the end of every transfer to signal the Source that the application has received all the data it expected. The application should send this after receiving a TWRC_XFERDONE or TWRC_CANCEL.

No special set up or action required. Be sure to correctly track which state the Source will be in as a result of your action. Be aware of the value in pPendingXfers->Count both before and after the operation. Invoking this operation causes the loss of data that your user may not expect to be lost. Be very careful and prudent when using this operation.


Source

Option #1) Fill pPendingXfers->Count with the number of transfers the Source is ready to supply to the application, upon demand. If pPendingXfers->Count > 0 (or equals -1), transition to State 6 and await initiation of the next transfer by the application. If pPendingXfers->Count == 0, transition all the way back to State 5 and await the next acquisition.

Option #2) Preempt the acquired data that is next in line for transfer to the application (pending transfers can be thought of as being pushed onto a FIFO queue as acquired and popped off the queue when transferred). Decrement pPendingXfers->Count. If already acquired, discard the data for the preempted transfer. Update pPendingXfers->Count with the new number of pending transfers. If this value is indeterminate, leave the value in this field at -1. Note: -1 is not a valid value for the number of audio snippets.

Option #3) Cancel the current transfer. Discard any local buffers or data involved in the transfer. Prepare the Source and the device for the next transfer. Decrement pPendingXfers->Count (don’t decrement if already zero or -1). If there is a transfer pending, return to State 6 and prepare the Source to begin the next transfer. If no transfer is pending, return to State 5 and await initiation of the next acquisition from the application or the user. Note: when DAT_XFERGROUP is set to DG_AUDIO, the Source will not go lower than State 6 based on the value of pPendingXfers->Count.

Note: If a Source supports simultaneous connections to more than one application, the Source should maintain a separate pPendingXfers structure for each application it is in-session with.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADDEST /* No such Source in-session with application */


See Also

DG_AUDIO / DAT_AUDIOFILEXFER / MSG_GETDG_AUDIO / DAT_AUDIONATIVEXFER / MSG_GET DG_CONTROL / DAT_PENDINGXFERS / MSG_GETDG_CONTROL / DAT_PENDINGXFERS / MSG_RESETDG_CONTROL / DAT_PENDINGXFERS / MSG_STOPFEEDERDG_CONTROL / DAT_XFERGROUP / MSG_SETDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GETDG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET

Capability - CAP_XFERCOUNT


Chapter 7

DG_CONTROL / DAT_PENDINGXFERS / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_PENDINGXFERS, MSG_GET, pPendingXfers);


Valid States

4 through 7

Description

Returns the number of transfers the Source is ready to supply to the application, upon demand. If DAT_XFERGROUP is set to DG_IMAGE, this is the number of images. If DAT_XFERGROUP is set to DG_AUDIO, this is the number of audio snippets for the current image. If there is no current image, this call must return TWRC_FAILURE / TWCC_SEQERROR.

Application


Source

Fill pPendingXfers->Count with the number of transfers the Source is ready to supply to the application, upon demand. This value should reflect the number of complete data blocks that have already been acquired or are in the process of being acquired.


If the Source is not sure how many transfers are pending, but is sure that the number is at least one, set pPendingXfers->Count to -1. A Source connected to a device with an automatic document feeder that cannot determine the number of pages in the feeder, or how many selections the user may make on each page, would respond in this way. A Source providing access to a series of images from a video camera or a data base may also respond this way.


-1 is not a valid value for pPendingXfers->Count.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE




See Also

DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERDG_CONTROL / DAT_PENDINGXFERS / MSG_RESETDG_CONTROL / DAT_PENDINGXFERS / MSG_STOPFEEDERDG_CONTROL / DAT_XFERGROUP / MSG_SET



Chapter 7

DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_PENDINGXFERS, MSG_RESET, pPendingXfers);


Valid States




6 only (State remains at 6)

Description

Sets the number of pending transfers in the Source to zero.

Application


No special set up or action required. Be aware of the state transition caused by this operation. Invoking this operation causes the loss of data that your user may not expect to be lost. Be very careful and prudent when using this operation. The application may need to use this operation if an error occurs within the application that necessitates breaking off all TWAIN sessions. This will get the application, Source Manager, and Source back to State 5 together.


The available audio snippets are discarded, but the Source remains in State 6.

Source

Set pPendingXfers->Count to zero. Discard any local buffers or data involved in any of the pending transfers.


Return to State 5 and await initiation of the next acquisition from the application or the user.


Remain in State 6.


Note: If a Source supports simultaneous sessions with more than one application, the Source should maintain a separate pPendingXfers structure for each application it is in-session with.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERDG_CONTROL / DAT_PENDINGXFERS / MSG_GETDG_CONTROL / DAT_PENDINGXFERS / MSG_STOPFEEDERDG_CONTROL / DAT_XFERGROUP / MSG_SET



Chapter 7

DG_CONTROL / DAT_PENDINGXFERS / MSG_STOPFEEDER

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_PENDINGXFERS, MSG_STOPFEEDER, pPendingXfers);


Valid States

6 only

Description

If CAP_AUTOSCAN is TRUE, this command will stop the operation of the scanner’s automatic feeder. No other action is taken.

Application

The DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET command stops a session (returning to State 5), but it also discards any images that have been captured by the scanner. The MSG_STOPFEEDER command solves this problem by stopping the feeder, but remaining in State 6. The application may then continue to transfer images, until pPendingXfers->Count goes to zero.

Source

This command should only perform successfully if CAP_AUTOSCAN is TRUE. If CAP_AUTOSCAN is FALSE, this command should return TWRC_FAILURE / TWCC_SEQERROR.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADDEST – no such Source in session with application.

TWCC_BADPROTOCOL - Source does not support operation.

TWCC_SEQERROR - Operation invoked in invalid state.

See Also

DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERDG_CONTROL / DAT_PENDINGXFERS / MSG_GETDG_CONTROL / DAT_PENDINGXFERS / MSG_RESET

Capabilities - CAP_AUTOSCAN


DG_CONTROL / DAT_SETUPFILEXFER / MSG_GET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_SETUPFILEXFER, MSG_GET, pSetupFile);

pSetupFile = A pointer to a TW_SETUPFILEXFER structure

Valid States

4 through 6

Description

Returns information about the file into which the Source has or will put the acquired DG_IMAGE or DG_AUDIO data.

Application


Source

Set the following:

pSetupFile->Format = format of destination file

(DG_IMAGE Constants: TWFF_TIFF, TWFF_PICT, TWFF_BMP, etc.)

(DG_AUDIO Constants: TWAF_WAV, TWAF_AIFF, TWAF_AU, etc.)

pSetupFile->FileName = name of file

(on Windows, include the complete path name)

pSetupFile->VRefNum = volume reference number

(Macintosh only)

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_BADPROTOCOL /* Source does not support file transfer */


See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDEFAULTDG_CONTROL / DAT_SETUPFILEXFER / MSG_RESETDG_CONTROL / DAT_SETUPFILEXFER / MSG_SET


Chapter 7

DG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET

Capabilities -ICAP_XFERMECH, ICAP_IMAGEFILEFORMAT,ACAP_XFERMECH


DG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDEFAULT

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_SETUPFILEXFER, MSG_GETDEFAULT, pSetupFile);


Valid States

4 through 6

Description

Returns information for the default DG_IMAGE or DG_AUDIO file.

Application


Source

Set the following:







(Macintosh only)

Return Codes

TWRC_SUCCESS

TWRC_FAILURE





Chapter 7

See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDG_CONTROL / DAT_SETUPFILEXFER / MSG_RESETDG_CONTROL / DAT_SETUPFILEXFER / MSG_SETDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET



DG_CONTROL / DAT_SETUPFILEXFER / MSG_RESET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_SETUPFILEXFER, MSG_RESET, pSetupFile);


Valid States

4 only

Description

Resets the current file information to the DG_IMAGE or DG_AUDIO default file information and returns that default information..

Application


Source

Set the following:







(Macintosh only)

Note: VRefNum should be set to reflect the default file only if it already exists). Otherwise, set this field to NULL.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE




Chapter 7


See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDEFAULTDG_CONTROL / DAT_SETUPFILEXFER / MSG_SETDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET



DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_SETUPFILEXFER, MSG_SET, pSetupFile);


Valid States

4 through 6

Description

Sets the file transfer information for the next file transfer. The application is responsible for verifying that the specified file name is valid and that the file either does not currently exist (in which case, the Source is to create the file), or that the existing file is available for opening and read/write operations. The application should also assure that the file format it is requesting can be provided by the Source (otherwise, the Source will generate a TWRC_FAILURE / TWCC_BADVALUE error).

Application

Set the following:







(Macintosh only)

Note: ICAP_XFERMECH or ACAP_XFERMECH (depending on the value of DAT_XFERGROUP) must have been set to TWSXdata) and return TWRC_FAILURE with TWCC_BADVALUE. If the format and file name are OK, but a file error occurs when trying to open the file (other than "file does not existö), return TWCC_BADVALUE and set up to use the default file. If the specified file does not exit, create it. If the file exists and has data in it, overwrite the existing data starting with the first byte of the file.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE




Chapter 7

TWCC_BADVALUE /* Source cannot comply with one of the */

/* settings */


See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDEFAULTDG_CONTROL / DAT_SETUPFILEXFER / MSG_RESETDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET




Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_SETUPMEMXFER, MSG_GET, pSetupMem);

pSetupMem = A pointer to a TW_SETUPMEMXFER structure.

Valid States

4 through 6

Description

Returns the Source’s preferred, minimum, and maximum allocation sizes for transfer memory buffers. The application using buffered memory transfers must use a buffer size between MinBufSize and MaxBufSize in their TW_IMAGEMEMXFER.Memory.Length when using the DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation. Sources may return a more efficient preferred value in State 6 after the image size, etc. has been specified.

Application


Source

Set the following:

pSetupMem->MinBufSize = minimum usable buffer size,in bytes

pSetupMem->MaxBufSize = maximum usable buffer size,in bytes (-1 means an indeterminately large buffer is acceptable)

pSetupMem->Preferred = preferred transfer buffer size, in bytes

If the Source doesn’t care about the size of any of these specifications, set the field(s) to TWON_DONTCARE32. This signals the application that any value for that field is OK with the Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE




Chapter 7

See Also

DG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET

Capabilities - ICAP_COMPRESSION, ICAP_XFERMECH


DG_CONTROL / DAT_STATUS / MSG_GET(from Application to Source Manager)

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_STATUS, MSG_GET, pSourceStatus);

pSourceStatus = A pointer to a TW_STATUS structure.

Valid States

2 through 7

Description

Returns the current Condition Code for the Source Manager.

Application

NULL references the operation to the Source Manager.

Source Manager

Fills pSourceStatus->ConditionCode with its current Condition Code. Then, it will clear its internal Condition Code so you cannot issue a status inquiry twice for the same error (the information is lost after the first request).

Return Codes

TWRC_SUCCESS /* This operation must succeed */

TWRC_FAILURE


See Also

Return Codes and Condition Codes (Chapter 11, "Return Codes and Condition Codes”)


Chapter 7

DG_CONTROL / DAT_STATUS / MSG_GET (from Application to Source)

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_STATUS, MSG_GET, pSourceStatus);

pSourceStatus = A pointer to a TW_STATUS structure.

Valid States

4 through 7

Description

Returns the current Condition Code for the specified Source.

Application

pDest references a copy of the targeted Source’s identity structure.

Source

Fills pSourceStatus->ConditionCode with its current Condition Code. Then, it will clear its internal Condition Code so you cannot issue a status inquiry twice for the same error (the information is lost after the first request).

Fills pSourceStatus->Data with its current custom code. If there is no custom code, the value must be 0.

Return Codes

TWRC_SUCCESS /* This operation must succeed */

TWRC_FAILURE


See Also

Return Codes and Condition Codes (Chapter 11, "Return Codes and Condition Codes”)


DG_CONTROL / DAT_STATUSUTF8 / MSG_GET

Call

DSM_Entry(pOrigin, NULL, DG_CONTROL, DAT_STATUSUTF8, MSG_GET, pStatusUtf8);

pStatusUtf8 = pointer to a TW_STATUSUTF8 structure.

Valid States

3 through 7

Description

Translate the contents of a TW_STATUS structure received from a Source into a localized UTF-8 encoded string.

Application

This operation can be called at anytime, with the contents of any TW_STATUS structure that it has received from the Source. The Source returns a value indicating the number of bytes (not characters) of data, including the terminating NUL byte. It also returns a handle to a UTF-8 encoded string, which the Application must lock before accessing, and which it must unlock and free when it is done.

Source

Translates the full contents of a TW_STATUS structure into a localized UTF-8 encode string, returning back a handle to that string, and the number of bytes (not characters) in the string, including the terminating NUL byte.

The Source returns a generic message if it is asked to return a string for a status code that it does not recognize.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADVALUE// something is wrong with &StatusUtf8

See Also



Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_USERINTERFACE, MSG_DISABLEDS, pUserInterface);

pUserInterface = A pointer to a TW_USERINTERFACE structure.

Valid States


Description

This operation causes the Source’s user interface, if displayed during the DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS operation, to be lowered. The Source is returned to State 4, where capability negotiation can again occur. The application can invoke this operation either because it wants to shut down the current session, or in response to the Source “posting” a MSG_CLOSEDSREQ event to it. Rarely, the application may need to close the Source because an error condition was detected.

Application

References the same pUserInterface structure as during the MSG_ENABLEDS operation. This implies that the application keep a copy of this structure locally as long as the Source is enabled.

If the application did not display the Source’s built-in user interface, it will most likely invoke this operation either when all transfers have been completed or aborted (TW_PENDINGXFERS.Count = 0).

Source

If the Source’s user interface is displayed, it should be lowered. The Source returns to State 4 and is again available for capability negotiation.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE


TWCC_SEQERROR /* Operation invoked in */ /* invalid state */

See Also

DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQDG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS


Event loop information (in Chapter 3, "Application Implementation”)


Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_USERINTERFACE, MSG_ENABLEDS, pUserInterface);

pUserInterface = A pointer to a TW_USERINTERFACE structure

Valid States


Description

This operation causes three responses in the Source:

• Places the Source into a “ready to acquire” condition. If the application raises the Source’s user interface (see #2, below), the Source will wait to assert MSG_XFERREADY until the “GO” button in its user interface or on the device is clicked. If the application bypasses the Source’s user interface, this operation causes the Source to become immediately “armed”. That is, the Source should assert MSG_XFERREADY as soon as it has data to transfer.

• The application can choose to raise the Source’s built-in user interface, or not, using this operation. The application signals the Source’s user interface should be displayed by setting pUserInterface->ShowUI to TRUE. If the application does not want the Source’s user interface to be displayed, or wants to replace the Source’s user interface with one of its own, it sets pUserInterface->ShowUI to FALSE. If activated, the Source’s user interface will remain displayed until it is closed by the user or explicitly disabled by the application (see Note).

• Terminates Source’s acceptance of “set capability” requests from the application. Capabilities can only be negotiated in State 4 (unless special arrangements are made using the CAP_EXTENDEDCAPS capability). Values of capabilities can still be inquired in States 5 through 7.

Note: Once the Source is enabled, the application must begin sending the Source every event that enters the application’s main event loop. The application must continue to send the Source events until it disables (MSG_DISABLEDS) the Source. This is true even if the application chooses not to use the Source’s built-in user interface.

Application

Set pUserInterface->ShowUI to TRUE to display the Source’s built-in user interface, or to FALSE to place the Source in an “armed” condition so that it is immediately prepared to acquire data for transfer. Set ShowUI to FALSE only if bypassing the Source’s built-in user interface—that is, only if the application is prepared to handle all user interaction necessary to acquire data from the selected Source.

Sources are not required to be enabled without showing their User Interface (i.e. TW_USERINTERFACE.ShowUI = FALSE). If a Source does not support ShowUI = FALSE, they will continue to be enabled just as if ShowUI = TRUE, but return TWRC_CHECKSTATUS. The application can check for this Return Code and continue knowing the Source’s User Interface is being displayed.


Watch the value of pUserInterface->ModalUI after the operation has completed to see if the Source’s user interface is modal or modeless.

The application must maintain a local copy of pUserInterface while the Source is enabled.

Windows only—The application should place a handle (hWnd) to the window acting as the Source’s parent into pUserInterface->hParent.

Macintosh only—Set pUserInterface->hParent to NULL.

Note: Application should establish that the Source can supply compatible ICAP_PIXELTYPEs and ICAP_BITDEPTHs prior to enabling the Source. The application must verify that the Source can supply data of a type it can consume. If this operation fails, the application should notify the user that the device and application are incompatible due to data type mismatch. If the application diligently sets SupportedGroups in its identity structure before it tries to open the Source, the Source Manager will, in the Select Source dialog or through the MSG_GETFIRST/MSG_GETNEXT mechanism, filter out the Sources that don’t match these SupportedGroups.

Source

If pUserInterface->ShowUI is TRUE, the Source should display its user interface and wait for the user to initiate an acquisition. If pUserInterface->ShowUI is FALSE, the Source should immediately begin acquiring data based on its current configuration (a device that requires the user to push a button on the device, such as a hand-scanner, will be “armed” by this operation and will assert MSG_XFERREADY as soon as the Source has data ready for transfer). The Source should fail any attempt to set a capability value (TWRC_FAILURE / TWCC_SEQERROR) until it returns to State 4 (unless an exception approval exists via a CAP_EXTENDEDCAPS agreement).

Set pUserInterface->ModalUI to TRUE if your built-in user interface is modal. Otherwise, set it to FALSE.

Note: Note: While the Source's user interface is raised, the Source is responsible for presenting the user with appropriate progress indicators regarding the acquisition and transfer processes unless the application has set CAP_INDICATORS to FALSE.

Note: It is strongly recommended that all Sources support being enabled without their User Interface if the application requests (TW_USERINTERFACE.ShowUI = FALSE). But if your Source cannot be used without its User Interface, it should enable showing the Source User Interface (just as if ShowUI = TRUE) but return TWRC_CHECKSTATUS. All Sources, however, must support the CAP_UICONTROLLABLE. This capability reports whether or not a Source allows ShowUI = FALSE. An application can use this capability to know whether the Source-supplied user interface can be suppressed before it is displayed.

Return Codes

TWRC_SUCCESS

TWRC_CHECKSTATUS /* Source cannot enable */

/* without User Interface */


Chapter 7

/* so it enabled with the */

/* User Interface. */

TWRC_FAILURE


TWCC_LOWMEMORY /* Not enough memory to open */ /* the Source */

TWCC_OPERATIONERROR /* Internal Source error; */ /* handled by the Source */


TWCC_NOMEDIA /* Source has nothing to capture */

See Also

DG_CONTROL / DAT_NULL / MSG_CLOSEDSREQDG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS

Capability - CAP_INDICATORS

Event loop information (in Chapter 3, "Application Implementation”)


DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDSUIONLY

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_USERINTERFACE,MSG_ENABLEDSUIONLY, pUserInterface);

pUserInterface = A pointer to a TW_USERINTERFACE structure.

Valid States

4 only (transitions to State 5, if successful)

Description

This operation is very similar to DG_CONTROL/ DAT_USERINTERFACE/ MSG_ENABLEDS operation except that no image transfer will take place. This operation is used by applications that wish to display the source user interface to allow the user to manipulate the sources current settings for DPI, paper size, etc. but not acquire an image. The ShowUI member of the TW_USERINTERFACE structure is ignored since this operations only purpose is to display the source UI. The other members of the TW_USERINTERFACE structure have the same meaning as in the DG_CONTROL/ DAT_USERINTERFACE/ MSG_ENABLEDS operation.

This operation has the following effects.

• The source transitions from state 4 to state 5. The source will display its user interface dialog but will not have a scan button (unless its only purpose is to preview the image).

• The application must begin sending the Source every event that enters the applications main event loop. This mechanism is the same as in the MSG_ENABLEDS operation.

• When the user hits OK or cancel from the source user interface dialog the source will send either MSG_CLOSEDSOK or MSG_CLOSEDSREQ Message.

• To close the source the application will respond back by sending a DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDS. This source closes the dialog and then transitions from state 5 back to state 4 .


Chapter 7

DG_CONTROL / DAT_XFERGROUP / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_CONTROL, DAT_XFERGROUP, MSG_GET, pXferGroup);

pXferGroup = A pointer to a TW_UINT32 value.

Valid States

4 through 6

Description

Returns the Data Group (the type of data) for the upcoming transfer. The Source is required to only supply one of the DGs specified in the SupportedGroups field of pOrigin.

Application

Should have previously (during a DG_CONTROL / DAT_PARENT / MSG_OPENDSM) set pOrigin. SupportedGroups to reflect the DGs the application is interested in receiving from a Source. Since DG_xxxx identifiers are bit flags, the application can perform a bitwise OR of DG_xxxx constants of interest to build the SupportedGroups field (this is appropriate when more kinds of data than DG_IMAGE are available).

Note: Version 1.x of the Toolkit defines DG_IMAGE and DG_AUDIO as the sole Data Groups (DG_CONTROL is masked from any processing of SupportedGroups). Future versions of TWAIN may define support for other DGs.

Source

Set pXferGroup to the DG_xxxx constant that identifies the type of data that is ready for transfer from the Source (DG_IMAGE is the only non-custom Data Group defined in TWAIN version 1.x).

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_CONTROL / DAT_XFERGROUP / MSG_SET


DG_CONTROL / DAT_XFERGROUP / MSG_SET

Call

DSM_Entry (pOrigin, pDest, DG_CONTROL, DAT_XFERGROUP, MSG_SET, pXFerGroup);

pXferGroup = A pointer to a TW_UINT32 value.

Valid States

6 only

Description

The transfer group determines the kind of data being passed from the Source to the Application. By default a TWAIN Source must default to DG_IMAGE. Currently the only other data group supported is DG_AUDIO, which is a feature supported by some digital cameras.

An Application changes the data group in State 6 to indicate that it wants to transfer any audio data associated with the current image. The transfers follow the typical TWAIN State 6 – State 7 – State 6 pattern for each audio snippet transferred. When the application is done transferring audio data it must change back to DG_IMAGE in order to move on to the next image or to end the transfers and return to State5.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADDEST – no such Source in session with application.



See Also

DG_CONTROL / DAT_XFERGROUP/ MSG_GET


Chapter 7

DG_IMAGE / DAT_CIECOLOR / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_CIECOLOR, MSG_GET, pCIEColor);

pCIEColor = A pointer to a TW_CIECOLOR structure.

Valid States

4 through 6

Description

Background - The DAT_CIECOLOR data argument type is used to communicate the parametrics for performing a transformation from any arbitrary set of tri-stimulus values into CIE XYZ color space. Color data stored in this format is more readily manipulated mathematically than some other spaces. See Appendix A for more information about the definitions and data structures used to describe CIE color data within TWAIN.

This operation causes the Source to report the currently active parameters to be used in converting acquired color data into CIE XYZ.

Application

Prior to invoking this operation, the application should establish that the Source can provide data in CIE XYZ form. This can be determined by invoking a MSG_GET on ICAP_PIXELTYPE. If TWPT_CIEXYZ is one of the supported types, then these operations are valid. The application can specify that transfers should use the CIE XYZ space by invoking a MSG_SET operation on ICAP_PIXELTYPE using a TW_ONEVALUE container structure whose value is TWPT_CIEXYZ.

No special set up is required. Invoking this operation following the transfer (after the Source is back in State 6) will guarantee that the exact parameters used to convert the image are reported.

Source

Fill pCIEColor with the current values applied in any conversion of image data to CIE XYZ. If no values have been set by the application, fill the structure with either the values calculated for this image or the Source’s default values, whichever most accurately reflect the state of the Source.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support the */ /* CIE descriptors */



See Also

Capability - ICAP_PIXELTYPE

Appendix A, "TWAIN Articles “


Chapter 7

DG_IMAGE / DAT_EXTIMAGEINFO / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_EXTIMAGEINFO,MSG_GET,pExtImageInfo);

pExtImageInfo = A pointer to a TW_EXTIMAGEINFO structure.

Valid States

7 only, after receiving TWRC_XFERDONE

Description

This operation is used by the application to query the data source for extended image attributes, .e.g. bar codes found on a page. The extended image information will be returned in a TW_EXTIMAGEINFO structure.

Application

To query extended image information, set the pExtImageInfo fields as follows:

The Application will allocate memory for the necessary container structure, the source will fill the values, and then application will free it up.

pExtImageInfo->NumInfos = Desired number of information;

pExtImageInfo->Info[0].InfoID = TWEI_xxxx;

pExtImageInfo->Info[1].InfoID = TWEI_xxxx;

Source

If the application requests information that the Source does not recognize, the Source should put TWRC_INFONOTSUPPORTED in the RetCode field of TW_INFO structure.

pExtImageInfo->Info[0].RetCode = TWRC_INFONOTSUPPORTED;

If you support the capability, fill in the fields allocating extra memory if necessary. For example, for TWEI_BARCODEX:

pExtImageInfo->Info[0].RetCode = TWRC_SUCCESS;

pExtImageInfo->Info[0].ItemType = TWTY_UINT32;

pExtImageInfo->Info[0].NumItems = 1;

pExtImageInfo->Info[0].Item = 20;

For TWEI_FORMTEMPLATEMATCH:

pExtImageInfo->Info[0].RetCode = TWRC_SUCCESS;

pExtImageInfo->Info[0].ItemType = TWTY_STR255;


pExtImageInfo->Info[0].NumItems = 1;

For handle (Application set TWMF_HANDLE),

pExtImageInfo->Info[0].Item = GlobalAlloc( GHND, sizeof(TW_STR255) );

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support extended image */

/* information */

TWCC_SEQERROR /* Not State 7, or in State 7 but TWRC_XFERDONE */

/* has not been received yet */


See Also

Capability ICAP_EXTIMAGEINFO, ICAP_SUPPORTEDEXTIMAGEINFO


Chapter 7

DG_IMAGE / DAT_GRAYRESPONSE / MSG_RESET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_GRAYRESPONSE, MSG_RESET, pResponse);

pResponse = A pointer to a TW_GRAYRESPONSE structure.

Valid States

4 only

Description

Background - The two DAT_GRAYRESPONSE operations allow the application to specify a transfer curve that the Source should apply to the grayscale it acquires. This curve should be applied to the data prior to transfer. The Source should maintain an “identity response curve” to be used when it is MSG_RESET.

The MSG_RESET operation causes the Source to use its “identity response curve.” The identity curve causes no change in the values of the captured data when it is applied.

Application

No special action.

Source

Apply the identity response curve to all future grayscale transfers. This means that the Source will transfer the grayscale data exactly as acquired.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support */ /* grayscale response curves */


See Also





Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_GRAYRESPONSE, MSG_SET, pResponse);

pResponse = A pointer to a TW_GRAYRESPONSE structure.

Valid States

4 only

Description

Background - The two DAT_GRAYRESPONSE operations allow the application to specify a transfer curve that the Source should apply to the grayscale it acquires. This curve should be applied to the data prior to transfer. The Source should maintain an “identity response curve” to be used when it is MSG_RESET. This identity curve should cause no change in the values of the data it is applied to.

This operation causes the Source to transform any grayscale data according to the response curve specified.

Application

All three elements of the response curve for any given index should hold the same value (the curve is stored in a TW_ELEMENT8 which contains three “channels” of data). The Source may not support this operation. The application should be diligent to examine the return code from this operation.

Source

Apply the specified response curve to all future grayscale transfers. The transformation should be applied before the data is transferred.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support */ /* grayscale response curves */


See Also

DG_IMAGE / DAT_GRAYRESPONSE / MSG_RESET



Chapter 7

DG_IMAGE / DAT_ICCPROFILE / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_ICCPROFILE,MSG_GET,pICCProfile);

pICCProfile = A pointer to a TW_MEMORY structure.

Valid States

6 or 7

Description

This operation provides the application with the ICC profile associated with the image which is about to be transferred (state 6) or is being transferred (state 7).

Application

The application can use the operation to retrieve an ICC profile associated with image data. This profile could then be used to transform the image to sRGB or to embed into a JPEG or TIFF file that the application is writing. If the application is having the source write the file (ICAP_XFERMECH of TWSX_FILE), then there is no need to call this triplet and the capability ICAP_ICCPROFILE should be used. It is important that the application not allocate the memory itself. Although a TW_MEMORY structure is used, the memory is always allocated by the source. The application should set the entire structure to zero. Note that not all sources will have profiles and some might have profiles for color data but not for grayscale data.

The profile returned always applies to the current data being transferred and not the image being currently scanned. This distinction is important for scanners that buffer pages since the data being transferred is most likely not the image being currently scanned.

For optimization, it is recommended that applications attempt to only call this on an as needed basis. In general, the application calls this once for each batch. However, it is important to note any changes in the pixeltype during a batch because changes in pixeltype will mandata a change in profile. While most scanners will not change the pixeltype int eh middle of a batch, those with job control sheets may do so.

Source

Allocates the TheMem member and sets the Flags member to have TWFM_DSOWNS. Fills in the Length member.

It is recommended that sources obey platform specific rules about locations for profile files. When possible, it is desirable to store the profiles in the platform specific location and then to read that profile and send the data back to the location.

See Also

Capability ICAP_ICCPROFILE


The new ICAP_PIXELTYPE values are:

TWPT_CIELABTWPT_SRGB Specifies that the data coming back has been calibrated to sRGB

If a source supports TWPT_SRGB, it must also support TWPT_RGB for backwards compatibility. If it only has sRGB data, then it should still support TWPT_RGB and pass back its sRBG data in that mode.


Chapter 7

DG_IMAGE / DAT_IMAGEFILEXFER / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGEFILEXFER, MSG_GET, NULL);

This operation acts on NULL data. File information can be set with the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation.

Valid States

6 only (Transitions to State 7, if successful. Remains in State 7 until MSG_ENDXFER operation.)

Description

This operation is used to initiate the transfer of an image from the Source to the application via the disk-file transfer mechanism. It causes the transfer to begin.

Application

No special set up or action required. Application should have already invoked the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation unless the Source’s default transfer format and file name (typically, TWAIN.TMP) are acceptable to the application. The application need only invoke this operation once per image transferred.

Note: If the application is planning to receive multiple images from the Source while using the Source’s default file name, the application should plan to pause between transfers and copy the file just written. The Source will overwrite the file unless it is instructed to write to a different file.

Note: Applications can specify a unique file for each transfer using DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation in State 6 or 5 (and 4, of course).

Source

Acquire the image data, format it, create any appropriate header information, and write everything into the file specified by the previous DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation, and close the file.

Handling Possible File Conditions:

• If the application did not set conditions up using the DAT_SETUPFILEXFER / MSG_SET operation during this session, use your own default file name, file format, and location for the created file.

• If the specified file already exists, overwrite the file in place.

• If the specified file does not exist, create the file.

• If the specified file exists and cannot be accessed, or a system error occurs while writing the file, report the error to the user and return TWRC_FAILURE with TWCC_OPERATIONERROR.


Stay in State 6. The file contents are invalid. The image whose transfer failed is still a pending transfer so do not decrement TW_PENDINGXFERS.Count.

• If the file is written successfully, return TWRC_XFERDONE.

• If the user cancels the transfer, return TWRC_CANCEL.

Return Codes

TWRC_XFERDONE

TWRC_CANCEL

TWRC_FAILURE


TWCC_OPERATIONERROR /* Failure in the Source -- */ /* transfer invalid */


/* The following introduced for 2.0 or higher */

TWCC_INTERLOCK /* Cover or door is open */

TWCC_DAMAGEDCORNER /* Document has a damaged corner */

TWCC_FOCUSERROR /* Focusing error during document capture */

TWCC_DOCTOOLIGHT /* Document is too light */

TWCC_DOCTOODARK /* Document is too dark */


See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_SETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEINFO / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GET,

Capabilities - ICAP_XFERMECH, ICAP_IMAGEFILEFORMAT


Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGEINFO, MSG_GET,pImageInfo);

pImageInfo = A pointer to a TW_IMAGEINFO structure.

Valid States

6 and 7 (State 7 only after receiving TWRC_XFERDONE)

Description

When called in State 6, this operation provides to the application general image description information about the image about to be transferred.

When called in State 7, this operation provides the Application with specific image description information about the current image that has just been transferred. It is important during a Memory transfer to call this triplet only after TWRC_XFERDONE is received, since that is the only time the Source will know all the final image information.

The same data structure type is used regardless of the mechanism used to transfer the image (Native, Disk File, or Buffered Memory transfer).

Application

The Application can use this operation to check the parameters of the image before initiating the transfer during State 6, or to clarify image parameters during State 7 after the transfer is complete.

Applications may inform Sources that they accept -1 value for ImageHeight/ImageWidth by setting the ICAP_UNDEFINEDIMAGESIZE capability to TRUE.

Should the Application decide to invoke any Source features that allow the image description information to change during scanning (such as ICAP_UNDEFINEDIMAGESIZE) and still wish to transfer in Buffered memory mode, a DG_CONTROL/DAT_IMAGEINFO/MSG_GET call must be made in State 7 after receiving TWRC_XFERDONE to properly interpret the image data. This is not the default behavior of the Source.

Note that the speed at which the Application supplies buffers may determine the scanning speed.

Source

During State 6 - Fills in all fields in pImageInfo. All fields are filled in as you would expect with the following exceptions:

XResolution or YResolution

Set to -1 if the device creates data with no inherent resolution (such as a digital camera).


ImageWidth

Set to -1 if the image width to be acquired is unknown (such as when using a hand-held scanner and dragging left-to-right) , and the Application has set ICAP_UNDEFINEDIMAGESIZE to TRUE. In this case the Source must transfer the image in tiles.

ImageLength

ImageLength—Set to -1 if the image length to be acquired is unknown (such as when using a hand-held scanner and dragging top-to-bottom), and the Application has set ICAP_UNDEFINEDIMAGESIZE to TRUE.

During State 7 - Fills in all fields in pImageInfo. All fields are filled in as during State 6, except ImageWidth and ImageLength MUST be valid. Source shall return TWRC_SEQERROR if call is made before TWRC_XFERDONE is sent.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_IMAGEFILEXFER / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GETDG_IMAGE / DAT_IMAGENATIVEXFER / MSG_GET

Capabilities - ICAP_BITDEPTH, ICAP_COMPRESSION, ICAP_PIXELTYPE, ICAP_PLANARCHUNKY, ICAP_XRESOLUTION, ICAP_YRESOLUTION


Chapter 7

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGELAYOUT, MSG_GET, pImageLayout);

pImageLayout = A pointer to a TW_IMAGELAYOUT structure.

Valid States

4 through 6

Description

The DAT_IMAGELAYOUT operations control information on the physical layout of the image on the acquisition platform of the Source (e.g. the glass of a flatbed scanner, the size of a photograph, etc.).

The MSG_GET operation describes both the size and placement of the image on the original “page”. The coordinates on the original page and the extents of the image are expressed in the unit of measure currently negotiated for ICAP_UNITS (default is inches).

The outline of the image is expressed by a “frame.” The Left, Top, Right, and Bottom edges of the frame are stored in pImageLayout->Frame. These values place the frame within the original page. All measurements are relative to the page’s “upper-left” corner. Define “upper-left” by how the image would appear on the computer’s screen before any rotation or other position transform is applied to the image data. This origin point will be apparent for most Sources (although folks working with satellites or radio telescopes may be at a bit of a loss).

Finally pImageLayout optionally includes information about which frame on the page, which page within a document, and which document the image belongs to. These fields were included mostly for future versions which could merge more than one type of data. A more immediate use might be for an application that needs to keep track of which frame on the page an image came from while acquiring from a Source that can supply more than one image from the same page at the same time. The information in this structure always describes the current image. To set multiple frames for any page simultaneously, reference ICAP_FRAMES.

Application

No special set up or action required, unless the current units of measure are unacceptable. In that case, the application must re-negotiate ICAP_UNITS prior to invoking this operation. Remember to do this in State 4—the only state wherein capabilities can be set or reset.

Beyond supplying possibly interesting position information on the image to be transferred, the application can use this structure to constrain the final size of the image and to relate the image within a series of pages or documents (see the DG_IMAGE / DAT_IMAGELAYOUT / MSG_SET operation).


Source

Fill all fields of pImageLayout. Most Sources will set FrameNumber, PageNumber, and DocumentNumber to 1.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULTDG_IMAGE / DAT_IMAGELAYOUT / MSG_RESETDG_IMAGE / DAT_IMAGELAYOUT / MSG_SET

Capabilities - Many such as ICAP_FRAMES, ICAP_MAXFRAMES, ICAP_UNITS


Chapter 7

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULT

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGELAYOUT, MSG_GETDEFAULT, pImageLayout);


Valid States

4 through 6

Description


This operation returns the default information on the layout of an image. This is the size and position of the image that will be acquired from the Source if the acquisition is started with the Source (and the device it is controlling) in its power-on state (for instance, most flatbed scanners will capture the entire bed).

Application


Source

Fill in all fields of pImageLayout with the device’s power-on origin and extents. Most Sources will set FrameNumber, PageNumber, and DocumentNumber to 1.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULTDG_IMAGE / DAT_IMAGELAYOUT / MSG_SET

Capabilities - ICAP_FRAMES, ICAP_MAXFRAMES, ICAP_UNITS


DG_IMAGE / DAT_IMAGELAYOUT / MSG_RESET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGELAYOUT, MSG_RESET, pImageLayout);


Valid States

4 only

Description


This operation sets the image layout information for the next transfer to its default settings.

Application

No special set up or action required. Ascertain the current settings of ICAP_ORIENTATION, ICAP_PHYSICALWIDTH, and ICAP_PHYSICALHEIGHT if you don’t already know this device’s power-on default values.

Source

Reset all the fields of the structure pointed at by pImageLayout to the device’s power-on origin and extents. There is an implied resetting of ICAP_ORIENTATION, ICAP_PHYSICALWIDTH, and ICAP_PHYSICALHEIGHT to the device’s power-on default values.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULTDG_IMAGE / DAT_IMAGELAYOUT / MSG_SET



Chapter 7

DG_IMAGE / DAT_IMAGELAYOUT / MSG_SET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGELAYOUT, MSG_SET, pImageLayout);


Valid States

4 only

Description


This operation sets the layout for the next image transfer. This allows the application to specify the physical area to be acquired during the next image transfer (for instance, a frame-based application would pass to the Source the size of the frame the user selected within the application—the helpful Source would present a selection region already sized to match the layout frame size).

If the application and Source have negotiated one or more frames through ICAP_FRAMES, the frame set with this operation will only persist until the transfer following this one. Otherwise, the frame will persist as the current frame for the remainder of the session (unless superseded by negotiation on ICAP_FRAMES or another operation on DAT_IMAGELAYOUT overrides it).

The application writer should note that setting these values is a request. The Source should first try to match the requested values exactly. Failing that, it should approximate the requested values as closely as it can—extents of the approximated frame should at least equal the requested extents unless the device cannot comply. The Source should return TWRC_CHECKSTATUS if the actual values set in pImageLayout->Frame are greater than or equal to the requested values in both extents. If one or both of the requested values exceed the Source’s available values, the Source should return TWRC_FAILURE with TWCC_BADVALUE. The application should check for these return codes and perform a MSG_GET to verify that the values set by the Source are acceptable. The application may choose to cancel the transfer if Source could not set the layout information closely enough to the requested values.

Application

Fill in all fields of pImageLayout. Especially important is the Frame field whose values are expressed in ICAP_UNITS. If the application doesn’t care about one or more of the other fields, be sure to set them to -1 to prevent confusion. If the application only cares about the extents of the Frame, and not about the origin on the page, set the Frame.Top and Frame.Left to zero. Otherwise, the application can specify the location on the page where the Source should begin acquiring the image, in addition to the extents of the acquired image.


Source

Use the values in pImageLayout as the Source’s current image layout information. If you are unable to set the device exactly to the values requested in the Frame field, set them as closely as possible, always snapping to a value that will result in a larger frame, and return TWRC_CHECKSTATUS to the application.

If the application has set Frame.Top and Frame.Left to a non-zero value , set the origin for the image to be acquired accordingly. If possible, the Source should consider reflecting these settings in the user interface when it is raised. For instance, if your Source presents a pre-scan image, consider showing the selection region in the proper location and with the proper size suggested by the settings from this operation.

If the requested values exceed the maximum size the Source can acquire, set the pImageLayout->Frame values used within the Source to the largest extent possible within the axis of the offending value. Return TWRC_FAILURE with TWCC_BADVALUE.

Return Codes

TWRC_SUCCESS

TWRC_CHECKSTATUS /* Source approximated the requested*/ /* values */

TWRC_FAILURE


TWCC_BADVALUE /* Specified Layout values illegal */ /* for Source */


See Also

DG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULTDG_IMAGE / DAT_IMAGELAYOUT / MSG_RESET



Chapter 7

DG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGEMEMFILEXFER, MSG_GET, pImageMemXfer);

pImageMemXfer = A pointer to a TW_IMAGEMEMXFER structure.

File format information can be set with the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation.

Valid States

6 only (Transitions to State 7, if successful. Remains in State 7 until MSG_ENDXFER operation.)

Description

This operation is used to initiate the transfer of an image from the Source to the application via the Memory-File transfer mechanism.

This operation supports the transfer of successive blocks of an image file from the Source into one or more main memory transfer buffers. These buffers are allocated and owned by the application. The application should repeatedly invoke this operation while TWRC_SUCCESS is returned by the Source.

Application

No special set up is required. The application should have already invoked the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation unless the Source’s default file format is acceptable to the application (the filename is not used, since this transfer is being done in memory). The DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation should be used to determine the valid range of sizes for transferring the image. The application only needs to invoke both of these operations once per image transferred.

The application will allocate one or more memory buffers to contain the data being transferred from the Source. The application may allocate enough buffer space to contain the entire image being transferred or, more commonly, use the transfer buffer(s) as a temporary holding area while the complete image is assembled elsewhere (on disk, for instance).

If the application sets up buffers that are either too small or too large, the Source will fail the operation returning TWRC_FAILURE/TWCC_BADVALUE.

Once the buffers have been set up, the application should fill pImageMemXfer->Memory.Length with the actual size (in bytes) of each memory buffer (which are, of course, all the same size).

Notes: Applications can specify a unique file format for each transfer using DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET in State 6 or 5 (and 4 also). Also note that although the images are being transferred in complete image formats, they are memory transfers, and will be chunked just like a DG_IMAGE / DAT_IMAGEMEMXFER / MSG_GET operation.


The size of the allocated buffer(s) should be homogeneous (don’t change buffer sizes during transfer). The size the application selects should be based on the information returned by the Source from the DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation. The application should do its best to allocate transfer buffers of the size “preferred” by the Source. This will enhance the chances for superior transfer performance. The buffer size must be between MinBufSize and MaxBufSize as reported by the Source.

There is no concept of striping or tiling when using this operation. Data is transferred in generic chucks, which, depending on the file format, may result in partial header or footer information being sent in any given transfer. Applications are advised to avoid parsing the image format data until all of the blocks have been transferred

Source

If the application did not set up the conditions via the DAT_SETUPFILEXFER / MSG_SET operation during this session, use the Source’s default file format for the transfer.

Prior to writing the first buffer, check pImageMemXfer->Memory.Length for the size of the buffer(s) the application has allocated. If the size lies outside the maximum or minimum buffer size communicated to the application during the DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation, return TWRC_FAILURE/TWCC_BADVALUE and remain in State 6.

If the buffer is of an acceptable size, fill in all fields of pImageMemXfer except pImageMemXfer->Memory. The Source must write the data block into the buffer referenced by pImageMemXfer->Memory.TheMem and store the actual number of bytes written into the buffer in pImageMemXfer->BytesWritten. Compressed and tiled data effects how the Source fills in these values.

Return TWRC_SUCCESS after successfully writing each buffer. Return TWRC_CANCEL if the Source needs to terminate the transfer before the last buffer is written (as when the user aborts the transfer from the Source’s user interface). Return TWRC_XFERDONE to signal that the last buffer has been written. Following completion of the transfer, either after all the data has been written or the transfer has been canceled, remain in State 7 until explicitly transitioned back to State 6 by the application (DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER).

If TWRC_FAILURE occurred on the first buffer, the session remains in State 6. If failing on a subsequent buffer, the session remains in State 7. The strip whose transfer failed is still pending.

Notes on Memory Usage: Following a canceled transfer, the Source should dispose of the image that was being transferred and assure that any temporary variable and local buffer allocations are eliminated. The Source should be wary of allocating large temporary buffers or variables. Doing so may disrupt or even disable the transfer process. The application should be aware of the possible needs of the Source to allocate such space, however, and consider allocating all large blocks of RAM needed to support the transfer prior to invoking this operation. This may be especially important for devices that create image transfers of indeterminate size—such as hand-held scanners.

Return Codes

TWRC_SUCCESS /* Source done transferring */

/* the specified block */

TWRC_XFERDONE /* Source done transferring */


Chapter 7

/* the specified image */

TWRC_CANCEL /* User aborted the transfer from */

/* the Source */

TWRC_FAILURE

TWCC_BADDEST /* No such Source in-session */

/* with application */

TWCC_BADVALUE /* Size of buffer did not */

/* match TW_SETUPMEMXFER */

TWCC_OPERATIONERROR /* Failure in the Source -- */

/* transfer invalid */

TWCC_SEQERROR /* Operation invoked in */

/* invalid state */








See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_SETDG_CONTROL / DAT_SETUPMEMXFER / MSG_GETDG_ IMAGE / DAT_IMAGEMEMXFER / MSG_GETDG_IMAGE / DAT_IMAGEINFO / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GET

Capabilities - ICAP_COMPRESSION, ICAP_XFERMECH, ICAP_IMAGEFILEFORMAT



Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGEMEMXFER, MSG_GET, pImageMemXfer);

pImageMemXfer = A pointer to a TW_IMAGEMEMXFER structure.

Valid States

6 and 7 (Transitions to State 7, if successful. Remains in State 7 until MSG_ENDXFER operation.)

Description

This operation is used to initiate the transfer of an image from the Source to the application via the Buffered Memory transfer mechanism.

This operation supports the transfer of successive blocks of image data (in strips or, optionally, tiles) from the Source into one or more main memory transfer buffers. These buffers (for strips) are allocated and owned by the application. For tiled transfers, the source allocates the buffers. The application should repeatedly invoke this operation while TWRC_SUCCESS is returned by the Source.

Application

The application will allocate one or more memory buffers to contain the data being transferred from the Source. The application may allocate enough buffer space to contain the entire image being transferred or, more commonly, use the transfer buffer(s) as a temporary holding area while the complete image is assembled elsewhere (on disk, for instance).

The size of the allocated buffer(s) should be homogeneous (don’t change buffer sizes during transfer). The size the application selects should be based on the information returned by the Source from the DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation. The application should do its best to allocate transfer buffers of the size “preferred” by the Source. This will enhance the chances for superior transfer performance. The buffer size must be between MinBufSize and MaxBufSize as reported by the Source. Further, the buffers must contain an even number of bytes. Memory buffers must be double-word aligned and should be padded with zeros at the end of each raster line.

If the application sets up buffers that are either too small or too large, the Source will fail the operation returning TWRC_FAILURE/TWCC_BADVALUE.

Once the buffers have been set up, the application should fill pImageMemXfer->Memory.Length with the actual size (in bytes) of each memory buffer (which are, of course, all the same size).

Windows only—The buffers should be allocated in global memory.


Chapter 7

Source

Prior to writing the first buffer, check pImageMemXfer->Memory.Length for the size of the buffer(s) the application has allocated. If the size lies outside the maximum or minimum buffer size communicated to the application during the DG_CONTROL / DAT_SETUPMEMXFER / MSG_GET operation, return TWRC_FAILURE/TWCC_BADVALUE and remain in State 6.

If the buffer is of an acceptable size, fill in all fields of pImageMemXfer except pImageMemXfer->Memory. The Source must write the data block into the buffer referenced by pImageMemXfer->Memory.TheMem. Store the actual number of bytes written into the buffer in pImageMemXfer->BytesWritten. Compressed and tiled data effects how the Source fills in these values.

Return TWRC_SUCCESS after successfully writing each buffer. Return TWRC_CANCEL if the Source needs to terminate the transfer before the last buffer is written (as when the user aborts the transfer from the Source’s user interface). Return TWRC_XFERDONE to signal that the last buffer has been written. Following completion of the transfer, either after all the data has been written or the transfer has been canceled, remain in State 7 until explicitly transitioned back to State 6 by the application (DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER).

If TWRC_FAILURE occurred on the first buffer, the session remains in State 6. If failing on a subsequent buffer, the session remains in State 7. The strip whose transfer failed is still pending.

Notes on Memory Usage: Following a canceled transfer, the Source should dispose of the image that was being transferred and assure that any temporary variable and local buffer allocations are eliminated. The Source should be wary of allocating large temporary buffers or variables. Doing so may disrupt or even disable the transfer process. The application should be aware of the possible needs of the Source to allocate such space, however, and consider allocating all large blocks of RAM needed to support the transfer prior to invoking this operation. This may be especially important for devices that create image transfers of indeterminate size—such as hand-held scanners.

Return Codes

TWRC_SUCCESS /* Source done transferring */ /* the specified block */

TWRC_XFERDONE /* Source done transferring */ /* the specified image */

TWRC_CANCEL /* User aborted the transfer from */ /* the Source */

TWRC_FAILURE


TWCC_BADVALUE /* Size of buffer did not */ /* match TW_SETUPMEMXFER */

TWCC_OPERATIONERROR /* Failure in the Source-- */ /* transfer invalid */









See Also

DG_CONTROL / DAT_SETUPMEMXFER / MSG_GETDG_IMAGE / DAT_IMAGEINFO / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDG_IMAGE / DAT_IMAGEMEMFILEXFER / MSG_GET

Capabilities - ICAP_COMPRESSION, ICAP_TILES, ICAP_XFERMECH


Chapter 7


Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_IMAGENATIVEXFER, MSG_GET, pHandle);

pHandle = A pointer to a variable of type TW_UINT32.

Windows - This 32 bit integer is a handle variable to a DIB (Device Independent Bitmap) located in memory.

Macintosh - This 32-bit integer is a handle to a Picture (a PicHandle). It is a QuickDraw picture located in memory.

Valid States

6 only (Transitions to State 7, if successful. Remains in State 7 until MSG_ENDXFER operation).

Description

Causes the transfer of an image’s data from the Source to the application, via the Native transfer mechanism, to begin. The resulting data is stored in main memory in a single block. The data is stored in Picture (PICT) format on the Macintosh and as a device-independent bitmap (DIB) under Microsoft Windows. The size of the image that can be transferred is limited to the size of the memory block that can be allocated by the Source.

Note: This is the default transfer mechanism. All Source’s support this mechanism. The Source will use this mechanism unless the application explicitly negotiates a different transfer mechanism with ICAP_XFERMECH.

Application

The application need only invoke this operation once per image. The Source allocates the largest block available and transfers the image into it. If the image is too large to fit, the Source may resize the image. Read the DIB header or check the picFrame in the Picture to determine if this happened. The application is responsible for deallocating the memory block holding the Native-format image.

Windows only—Set pHandle pointing to a handle to a device-independent bit map (DIB) in memory. The Source will allocate the image buffer and return the handle to the address specified..

Macintosh only—Set pHandle pointing to a handle to a Picture in memory. The Source will allocate the image buffer at the memory location referenced by the handle.

Note: This odd combination of pointer and handle to reference the image data block was used to assure that the allocated memory object would be relocatable under Microsoft Windows, Macintosh, and UNIX. A handle was required for this task on both the Macintosh and under Microsoft Windows; though pointers are inherently relocatable under UNIX. Rather than disturb the entry points convention that the data object is


always referenced by a pointer, it was decided to have that pointer reference the relocatable handle. A handle in UNIX is typecast to a pointer.

Source

Allocate a single block of memory to hold the image data and write the image data into it using the appropriate format for the operating environment. The source must assure that the allocated block will be accessible to the application. Place the handle of the allocated block in the TW_UINT32 pointed to by pHandle.

Microsoft Windows: Format the data block as a DIB. Use GlobalAlloc or equivalent under windows. Under 16 bit Microsoft Windows, place the handle in the low word of the TW_UINT32. The following assignment will work in either Win16 or Win32:

(HGLOBAL FAR *) pHandle = hDIB;

See the Windows SDK documentation under Structures: BIMAPINFO, BITMAPINFOHEADER, RGBQUAD. See also “DIBs and their use” by Ron Gery, in the Microsoft Development Library (MSDN CD).

Notes:

• Do not use BITMAPCOREINFO or BIMAPCOREHEADER as these are for OS/2 compatibility only.

• Always follow the BITMAPINFOHEADER with the color table and only save 1, 4, or 8 bit DIBs

• Color table entries are RGBQUADs, which are stored in memory as BGR not RGB.

• For 24 bit color DIBs, the “pixels” are also stored in BGR order, not RGB.

• DIBs are stored ‘upside-down’ - the first pixel in the DIB is the lower-left corner of the image, and the last pixel is the upper-right corner.

• DIBs can be larger than 64K, but be careful, a 24 bit pixel can straddle a 64K boundary!

• Pixels in 1, 4, and 8 bit DIBs are “always” color table indices, you must index through the color table to determine the color value of a pixel.

Macintosh: Format the data block as a PICT, preferably using standard system calls.

Microsoft Windows and Macintosh: If the allocation fails, it is recommended that you allow the user the option to re-size the image to fit within available memory or to cancel the transfer (assuming that the Source user interface is displayed). If the user chooses to cancel the transfer, return TWRC_CANCEL. If the user wants to re-size the image, the Source might choose to blindly crop the image, clip a selection region to the maximum supported size for the current memory configuration, or allow the user to re-acquire the image altogether. The user will usually feel more in control if you provide one or both of the last two options, but the first may make the most sense for your Source.

If the allocation fails and the image cannot be clipped, return TWRC_FAILURE and remain in State 6. Set the pHandle to NULL. The image whose transfer failed is still pending transfer. Do not decrement TW_PENDINGXFERS.Count.


Chapter 7

Return Codes

TWRC_XFERDONE /* Source done transferring the */ /* specified block */

TWRC_CANCEL /* User aborted the transfer */ /* within the Source */

TWRC_FAILURE

TWCC_BADDEST /* No such Source in session */ /* with application */

TWCC_LOWMEMORY /* Not enough memory for */ /* image--cannot crop to fit */

TWCC_OPERATIONERROR /* Failure in the Source-- */ /* transfer invalid */









See Also

DG_IMAGE / DAT_IMAGEINFO / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GET

Capability - ICAP_XFERMECH


DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_JPEGCOMPRESSION, MSG_GET, pCompData);

pCompData = A pointer to a TW_JPEGCOMPRESSION structure.

Valid States

4 through 6

Description

Causes the Source to return the parameters that will be used during the compression of data using the JPEG algorithms.

All the information that is reported by the MSG_GET operation will be available in the header portion of the JPEG data. Transferring JPEG-compressed data through memory buffers is slightly different than other types of buffered transfers. The difference is that the JPEG-compressed image data will be prefaced by a block of uncompressed information—the JPEG header. This header information contains all the information that is returned from the MSG_GET operation. The compressed image information follows the header. The Source should return the header information in the first transfer. The compressed image data will then follow in the second through the final buffer. If the application is allocating the buffers, it should assure that the buffer size for transfer of the header is large enough to contain the complete header.

Application

The application allocates the TW_JPEGCOMPRESSION structure.

Source

Fill pCompData with the parameters that will be applied to the next JPEG-compression operation. The Source must allocate memory for the contents of the pointer fields pointed to within the structure (i.e. QuantTable, HuffmanDC, and HuffmanAC).

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support JPEG */ /* data compression */



Chapter 7

See Also

DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDEFAULTDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_RESETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_SET

Capability - ICAP_COMPRESSION


DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDEFAULT

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_JPEGCOMPRESSION, MSG_GETDEFAULT, pCompData);


Valid States

4 through 6

Description

Causes the Source to return the power-on default values applied to JPEG-compressed data transfers.

Application

The application allocates the TW_JPEGCOMPRESSION structure.

Source

Fill in pCompData with the power-on default values. The Source must allocate memory for the contents of the pointer fields pointed to within the structure (i.e. QuantTable, HuffmanDC and HuffmanAC). The Source should maintain meaningful default values.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_RESETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_SET

Capabilities - ICAP_COMPRESSION and ICAP_JPEGQUALITY


Chapter 7

DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_RESET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_JPEGCOMPRESSION, MSG_RESET, pCompData);


Valid States

4 only

Description

Return the Source to using its power-on default values for JPEG-compressed transfers.

Application

No special action. May want to perform a MSG_GETDEFAULT if you’re curious what the new values might be.

Source

Use your power-on default values for all future JPEG-compressed transfers. The Source should maintain meaningful default values for all parameters.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDEFAULTDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_SET



DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_SET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_JPEGCOMPRESSION, MSG_SET, pCompData);


Valid States

4 only

Description

Allows the application to configure the compression parameters to be used on all future JPEG-compressed transfers during the current session. The application should have already established that the requested values are supported by the Source.

Application

Fill pCompData. Write TWON_DONTCARE16 into the numeric fields that don’t matter to the application. Write NULL into the table fields that should use the default tables as defined by the JPEG specification.

Source

Adopt the requested values for use with all future JPEG-compressed transfers. If a value does not exactly match an available value, match the value as closely as possible and return TWRC_CHECKSTATUS. If the value is beyond the range of available values, clip to the nearest value and return TWRC_FAILURE/TWCC_BADVALUE.

Return Codes

TWRC_SUCCESS

TWRC_CHECKSTATUS

TWRC_FAILURE


TWCC_BADVALUE /* illegal value specified */


See Also

DG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDEFAULTDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_RESET



Chapter 7

DG_IMAGE / DAT_PALETTE8 / MSG_GET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_PALETTE8, MSG_GET, pPalette);

pPalette = A pointer to a TW_PALETTE8 structure.

Valid States

4 through 6

Description

This operation causes the Source to report its current palette information. The application should assure that the Source can provide palette information by invoking a MSG_GET operation on ICAP_PIXELTYPE and checking for TWPT_PALETTE. If this pixel type has not been established as the type to be used for future acquisitions, the Source should respond with its default palette.

To assure that the palette information is wholly accurate, the application should invoke this operation immediately after completion of the image transfer. The Source may perform palette optimization during acquisition of the data and the palette it reports before the transfer will differ from the one available afterwards.

(In general, the DAT_PALETTE8 operations are specialized to deal with 8-bit data, whether grayscale or color (8-bit or 24-bit). Most current devices provide data with this bit depth. These operations allow the application to inquire a Source’s support for palette color data and set up a palette color transfer. See Chapter 8, "Data Types and Data Structures” for the definitions and data structures used to describe palette color data within TWAIN.)

Application

The application should allocate the pPalette structure for the Source.

Source

Fill pPalette with the current palette. If no palette has been specified or calculated, use the Source’s default palette (which may coincidentally be the current or default system palette).

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support */ /* palette color transfers */



See Also

DG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULTDG_IMAGE / DAT_PALETTE8 / MSG_RESETDG_IMAGE / DAT_PALETTE8 / MSG_SET



Chapter 7

DG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULT

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_PALETTE8, MSG_GETDEFAULT, pPalette);


Valid States

4 through 6

Description

This operation causes the Source to report its power-on default palette.

Application


Source

Fill pPalette with the default palette.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_PALETTE8 / MSG_GETDG_IMAGE / DAT_PALETTE8 / MSG_RESETDG_IMAGE / DAT_PALETTE8 / MSG_SET



DG_IMAGE / DAT_PALETTE8 / MSG_RESET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_PALETTE8, MSG_RESET, pPalette);


Valid States

4 only

Description

This operation causes the Source to dispose of any current palette it has and to use its default palette for the next palette transfer. A Source that always performs palette optimization may not use the default palette for the next transfer, but should dispose of its current palette and adopt the default palette for the moment, anyway. The application can check the actual palette information by invoking a MSG_GET operation immediately following the image transfer.

Application


Source

Fill pPalette with the default palette and use the default palette for the next palette transfer.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_PALETTE8 / MSG_GETDG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULTDG_IMAGE / DAT_PALETTE8 / MSG_SET



Chapter 7

DG_IMAGE / DAT_PALETTE8 / MSG_SET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_PALETTE8, MSG_SET, pPalette);


Valid States

4 only

Description

This operation requests that the Source adopt the specified palette for use with all subsequent palette transfers. The application should be careful to supply a palette that matches the bit depth of the Source. The Source is not required to adopt this palette. The application should be careful to check the return value from this operation.

Application

Fill pPalette with the desired palette. If writing grayscale information, write the same data into the Channel1, Channel2, and Channel3 fields of the Colors array. If NumColors != 256, fill the unused array elements with minimum (“black”) values.

Source

The Source should not return TWRC_SUCCESS unless it will actually use the requested palette. The Source should not modify the palette in any way until the transfer is complete. The palette should be used for all remaining palette transfers for the duration of the session.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE



See Also

DG_IMAGE / DAT_PALETTE8 / MSG_GETDG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULTDG_IMAGE / DAT_PALETTE8 / MSG_RESET




Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_RGBRESPONSE, MSG_RESET, pResponse);

pResponse = A pointer to a TW_RGBRESPONSE structure.

Valid States

4 only

Description

Causes the Source to use its “identity” response curves for future RGB transfers. The identity curve causes no change in the values of the captured data when it is applied. (Note that resetting the curves for RGB data does not reset any MSG_SET curves for other pixel types).

Note: The DAT_RGBRESPONSE operations allow the application to specify the transfer curves that the Source should apply to the RGB data it acquires. The Source should not support these operations unless it can provide data of pixel type TWPT_RGB. The Source need not maintain actual “identity response curves” for use with the MSG_RESET operation—once reset, the Source should transfer the RGB data as acquired from the Source. The application should be sure that the Source supports these operations before invoking them. The operations should only be invoked when the active pixel type is RGB (TWPT_RGB). SeeChapter 8, "Data Types and Data Structures” for information about the definitions and data structures used to describe the RGB response curve within TWAIN.

Application

No special action.

Source

Apply the identity response curve to all future RGB transfers. This means that the Source will transfer the RGB data exactly as acquired from the device.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support RGB */ /* response curves */

TWCC_BADVALUE /* Current pixel type is not */ /* TWPT_RGB */



Chapter 7

See Also

DG_IMAGE / DAT_RGBRESPONSE / MSG_SET



DG_IMAGE / DAT_RGBRESPONSE / MSG_SET

Call

DSM_Entry(pOrigin, pDest, DG_IMAGE, DAT_RGBRESPONSE, MSG_SET, pResponse);

pResponse = A pointer to a TW_RGBRESPONSE structure.

Valid States

4 only

Description

Causes the Source to transform any RGB data according to the response curves specified by the application.

Application

Fill all three elements of the response curve with the response curve data you want the Source to apply to future RGB transfers. The application should consider writing the same values into each element of the same index to minimize color shift problems.

The Source may not support this operation. The application should ensure that the current pixel type is TWPT_RGB and examine the return code from this operation.

Source

Apply the specified response curves to all future RGB transfers.

Return Codes

TWRC_SUCCESS

TWRC_FAILURE

TWCC_BADPROTOCOL /* Source does not support color */ /* response curves */

TWCC_BADVALUE /* Current pixel type is not RGB */


See Also




Chapter 7


8Data Types and Data Structures

Chapter ContentsNaming Conventions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-1Platform Dependent Definitions and Typedefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-3Definitions of Common Types. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7Data Structure Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-7Data Argument Types that Don’t Have Associated TW_Structures . . . . . . . . . . . . . . . . . . . . . 8-63Data Argument Types that Don’t Have Associated TW_Structures . . . . . . . . . . . . . . . . . . . . . 8-63Constants. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8-65

This section of the Specification is definitive and authoritative in its description of the TWAIN namespace and the numeric ids that go with each name in that space. If a discrepancy is found between this chapter and any C/C++ TWAIN.H definition file then the TWAIN.H file must be corrected.

A TWAIN.H definition file is provided with this toolkit, this file is specific to C/C++ solutions.

If a definition file for a previously unsupported language is submitted to the TWAIN Working Group, and if it passes review, then the salient points needed to recreate it will be added to this chapter. A definition file cannot be called TWAIN or said to support TWAIN unless it can be completely created following the information in this chapter.

Naming Conventions

Data Structures, Variables, Pointers and Handles

Data structures referenced by pData parameter in DSM_Entry callsAre prefixed by TW_ and followed by a descriptive name, in upper case. The name typically matches the call’s DAT parameter.Example: TW_USERINTERFACE

Fields in data structures (not containing pointers or handles)Typically, begin with a capital letter followed by mixed upper and lower case letters.


Chapter 8

Example: The MinBufSize, MaxBufSize, and Preferred fields in which are in the TW_SETUPMEMXFER structure.

Fields in data structures that contain pointers or handlesName starts with lower case “p” or “h” for pointer or handle followed by a typical field name with initial capital then mixed case characters.Example: pData, hContainer

Constants and Types

General-use constantsAre prefixed by TWON_ followed by the description of the constant’s meaning.Example: TWON_ARRAY, TWON_ONEVALUE

Specific-use constantsAre prefixed with TWxx_ where xx are two letters identifying the group to which the constant belongs.Example: TWTY_INT16, TWTY_STR32 are constants of the group TW Types

Common data typesRather than use the int, char, long, and other. types with their variations between compilers, TWAIN defines a group of types that are used to cast each data item used by the protocol. Types are prefixed and named exactly the same as TWAIN data structures, TW_ followed by a descriptive name, all in upper case characters.Example: TW_UINT32, TW_HANDLE

TWAIN.H internal constantsStarting with TWAIN 2.0 internal constants that are of special interest to TWAIN.H itself are used to improve the readability and maintainability of the file. They are prefixed with TWH_.

Custom Constants

Applications and Sources may define their own private (custom) constant identifiers for any existing constant group by assigning the constant a value greater than or equal to 0x8000. They may also define any new desired custom constant group. The consuming entity should check the originating entity’s TW_IDENTITY.ProductName when encountering a constant value greater than or equal to 0x8000 to see whether it can be recognized as a custom constant. Sources and applications should not assume that all entities will have such error checking built in, however.

The following are operation identifiers:

Data Groups Prefixed with DG_

Data Argument Types Prefixed with DAT_

Messages Prefixed with MSG_

Return codes Prefixed with TWRC_

Condition codes Prefixed with TWCC_

General capabilities Prefixed with CAP_


Image-specific capabilities Prefixed with ICAP_

Audio-specific capabilities Prefixed with ACAP_

As a general note, whenever the application or the Source allocates a TWAIN data structure, it should fill all the fields it is instructed to fill and write the default value (if one is specified) into any field it is not filling. If no default is specified, fill the field with the appropriate TWON_DONTCARExx constant where xx describes the size of the field in bits (bytes, in the case of strings). The TWON_ constants are described at the end of this chapter and defined in the TWAIN.H file.

Some fields return a value of -1 when the data to be returned is ambiguous or unknown. Applications and Sources must look for these special cases, especially when allocating memory. Examples of Fields with -1 values are found in TW_PENDINGXFERS (Count), TW_SETUPMEMXFER (MaxBufSize) and TW_IMAGEINFO (ImageWidth and ImageLength).

Platform Dependent Definitions and Typedefs

Single Compile

The TWAIN include file must only be referenced once for any compiled module. This is achieved by bracketing the contents of the entire file with the following:

#ifndef TWAIN

#define TWAIN

…contents of the TWAIN include file…

#endif /* TWAIN */

Platform Identification Macros

TWAIN supports multiple operating system platforms; it also can run with multiple compilers. The following macros are intended to help organize these combinations. Note that they focus more on the compilers than the platforms (cf: for the purposes of TWAIN GNU works the same on all operating systems).

/* Microsoft C/C++ Compiler */

#if defined(WIN32) || defined(WIN64) || defined (_WINDOWS)

#define TWH_CMP_MSC

#if defined(_WIN64) || defined(WIN64)

#define TWH_64BIT

#elif defined(WIN32) || defined(_WIN32)

#define TWH_32BIT

#endif


Chapter 8

/* Apple Compiler (which is GNU now) */

#elif defined(__APPLE__)

#define TWH_CMP_XCODE

#define TWH_32BIT

/* GNU C/C++ Compiler */

#elif defined(__GNUC__)

#define TWH_CMP_GNU

#if defined(__alpha__)\

||defined(__ia64__)\

||defined(__ppc64__)\

||defined(__s390x__)\

||defined(__x86_64__)

#define TWH_64BIT

#else

#define TWH_32BIT

#endif

/* Borland C/C++ Compiler */

#elif defined(__BORLAND__)

#define TWH_CMP_BORLAND

#define TWH_32BIT

/* Unrecognized */

#else

#error Unrecognized compiler

#endif

Platform Specific Typedefs

These definitions and typedefs are dependent on the compiler.

/* Win32 and Win64 systems */

#if defined(TWH_CMP_MSC) | defined(TWH_CMP_BORLAND)

typedef HANDLE TW_HANDLE;

typedef LPVOID TW_MEMREF;

typedef UINT_PTR TW_UINTPTR;

/* MacOS/X... */


#elif defined(TWH_CMP_XCODE)

#define PASCAL pascal

#define FAR

typedef Handle TW_HANDLE;

typedef char *TW_MEMREF;

#ifdef TWH_32BIT

//32 bit GNU

typedef unsigned long TW_UINTPTR;

#else

//64 bit GNU

typedef unsigned long long TW_UINTPTR;

#endif

/* Everything else... */

#else

#define PASCAL

#define FAR

typedef void* TW_HANDLE;

typedef void* TW_MEMREF;

typedef unsigned char BYTE;

#ifdef TWH_32BIT

//32 bit GNU


#else

//64 bit GNU


#endif

#endif

Platform Specific Byte Packing (Alignment)

In addition to the dependent definitions and typedefs TWAIN requires that the data alignment of all structures occurs on an agreed upon boundary. This prevents mismatches in the alignment of the data between the driver, the source manager and the application.

/* Set the packing: this occurs before any structures are defined */


Chapter 8

#ifdef TWH_CMP_MSC

#pragma pack (push, before_twain)

#pragma pack (2)

#elif TWH_CMP_GNU

#pragma pack (push, before_twain)

#pragma pack (2)

#elif TWH_CMP_BORLAND

#pragma option -a2

#elif TWH_CMP_XCODE

#if PRAGMA_STRUCT_ALIGN

#pragma options align=mac68k

#elif PRAGMA_STRUCT_PACKPUSH

#pragma pack (push, 2)

#elif PRAGMA_STRUCT_PACK

#pragma pack (2)

#endif

#elif

/* Restore the previous packing alignment: this occurs after all structures are defined */

#ifdef TWH_CMP_MSC

#pragma pack (pop, before_twain)

#elif TWH_CMP_GNUC

#pragma pack (pop, before_twain)

#elif TWH_CMP_BORLANDC

#pragma option –a.

#elif TWH_CMP_XCODE

#if PRAGMA_STRUCT_ALIGN

#pragma options align=reset

#elif PRAGMA_STRUCT_PACKPUSH

#pragma pack (pop)

#elif PRAGMA_STRUCT_PACK

#pragma pack()

#endif

#endif


Definitions of Common Types

String typestypedef unsigned char TW_STR32[34], FAR *pTW_STR32;typedef unsigned char TW_STR64[66], FAR *pTW_STR64;typedef unsigned char TW_STR128[130], FAR *pTW_STR128;typedef unsigned char TW_STR255[256], FAR *pTW_STR255;

On Windows: These include room for the strings and a NULL character.

On Macintosh: These include room for a length byte followed by the string.

Note: The TW_STR255 must hold less than 256 characters so the length fits in the first byte on Macintosh.

Numeric typestypedef char TW_INT8FAR *pTW_INT8; typedef short TW_INT16 FAR *pTW_INT16;typedef long TW_INT32 FAR *pTW_INT32;typedef unsigned char TW_UINT8 FAR *pTW_UINT8;typedef unsigned short TW_UINT16 FAR *pTW_UINT16;typedef unsigned long TW_UINT32 FAR *pTW_UINT32;typedef unsigned short TW_BOOL FAR *pTW_BOOL;

Fixed point structure typetypedef struct {

TW_INT16Whole;TW_UINT16Frac;

} TW_FIX32, FAR * pTW_FIX32;

Note: In cases where the data type is smaller than TW_UINT32, the data resides in the lower word.

Data Structure DefinitionsThis section provides descriptions of the data structure definitions.


Chapter 8

TW_ARRAYtypedef struct { TW_UINT16 ItemType; TW_UINT32 NumItems; TW_UINT8 ItemList[1];} TW_ARRAY, FAR * pTW_ARRAY;

Used by

TW_CAPABILITY structure (when ConType field specifies TWON_ARRAY)

Description

This structure stores a group of associated individual values which, when taken as a whole, describes a single “value” for a capability. The values need have no relationship to one another aside from being used to describe the same “value” of the capability. Such an array of values is useful to describe the CAP_SUPPORTEDCAPS list. This structure is used as a member of TW_CAPABILITY structures. Since this structure does not, therefore, exist “stand-alone” it is identified by a TWON_xxxx constant rather than a DAT_xxxx. This structure is related in function and purpose to TW_ENUMERATION, TW_ONEVALUE, and TW_RANGE.

Field Descriptions

ItemType The type of items in the array. The type is indicated by the constant held in this field. The constant is of the kind TWTY_xxxx. All items in the array have the same size.

NumItems How many items are in the array.

ItemList[1] This is the array. One value resides within each element of the array. Space for the array is not allocated inside this structure. The ItemList value is simply a placeholder for the start of the actual array, which must be allocated when the container is allocated. Remember to typecast the allocated array, as well as references to the elements of the array, to the type indicated by the constant in ItemType.

Ex:To set an item in a CAP_SUPPORTEDCAPS array…((TW_UINT16*)twarray.ItemList)[2] = ICAP_XFERMECH;


TW_AUDIOINFOtypedef struct { TW_STR255 Name; TW_UINT32 Reserved;} TW_AUDIOINFO, FAR * pTW_AUDIOINFO;

Used by

The DG_AUDIO / DAT_AUDIOINFO / MSG_GET operation

Description

-

Field Descriptions

Name Name of audio data

Reserved Reserved space


Chapter 8

TW_CAPABILITYtypedef struct { TW_UINT16 Cap; TW_UINT16 ConType; TW_HANDLE hContainer;} TW_CAPABILITY, FAR * pTW_CAPABILITY;

Used byDG_CONTROL / DAT_CAPABILITY / MSG_GETDG_CONTROL / DAT_CAPABILITY / MSG_GETCURRENTDG_CONTROL / DAT_CAPABILITY / MSG_GETDEFAULTDG_CONTROL / DAT_CAPABILITY / MSG_RESETDG_CONTROL / DAT_CAPABILITY / MSG_RESETALLDG_CONTROL / DAT_CAPABILITY / MSG_SET

Description

Used by an application either to get information about, or control the setting of a capability. The first field identifies the capability being negotiated (e.g., ICAP_BRIGHTNESS). The second specifies the format of the container (e.g., TWON_ONEVALUE). The third is a handle (HGLOBAL under Microsoft Windows) to the container itself.

The application always sets the Cap field. On MSG_SET, the application also sets the ConType and hContainer fields. On MSG_RESET, MSG_RESETALL, MSG_GET, MSG_GETCURRENT, and MSG_GETDEFAULT, the source fills in the ConType and hContainer fields.

It is always the application’s responsibility to free the container when it is no longer needed. On a MSG_GET, MSG_GETCURRENT, or MSG_GETDEFAULT, the source allocates the container but ownership passes to the application. On a MSG_SET, the application provides the container either by allocating it or by re-using a container created earlier.

On a MSG_SET, the Source must not modify the container and it must copy any data that it wishes to retain.

Field Descriptions

Cap The numeric designator of the capability (of the form CAP_xxxx, ICAP_xxxx, or ACAP_xxxx). e.g. ICAP_BRIGHTNESS. A list of these can be found in Chapter 9, "Capabilities” and in the TWAIN.H file.

ConType The type of the container referenced by hContainer. The container structure will be one of four types: TWON_ARRAY, TWON_ENUMERATION, TWON_ONEVALUE, or TWON_RANGE. One of these values, which types the container, should be entered into this field by whichever TWAIN entity fills in the container. When the application wants to set (MSG_SET) the Source’s capability, the application must fill in this field. When the application wants to get (MSG_GET) capability information from the Source, the Source must fill in this field.


hContainer References the container structure where detailed information about the capability is stored. When the application wants to set (MSG_SET) the Source’s capability, the application must provide the hContainer. When the application wants to get (MSG_GET) the Source’s capability information, the Source must allocate the space for the container. In either case, the application must release this space.


Chapter 8

TW_CIECOLORtypedef struct { TW_UINT16 ColorSpace TW_INT16 LowEndian; TW_INT16 DeviceDependent; TW_INT32 VersionNumber; TW_TRANSFORMSTAGE StageABC; TW_TRANSFORMSTAGE StageLMN; TW_CIEPOINT WhitePoint; TW_CIEPOINT BlackPoint; TW_CIEPOINT WhitePaper; TW_CIEPOINT BlackInk; TW_FIX32 Samples[1];} TW_CIECOLOR, FAR * pTW_CIECOLOR;

Used by

DG_IMAGE / DAT_CIECOLOR / MSG_GET

Description

Defines the mapping from an RGB color space device into CIE 1931 (XYZ) color space. For more in-depth information, please reference the PostScript Language Reference Manual, Second Edition, pp. 173-193. Note that the field names do not follow the conventions used elsewhere within TWAIN. This breach allows the identifiers shown here to exactly match those described in Appendix A, which was not written specifically for this Toolkit. Please also note that ColorSpace has been redefined from its form in Appendix A to use TWPT_xxxx constants defined in the TWAIN.H file.

This structure closely parallels the TCIEBasedColorSpace structure definition in Chapter A, "TWAIN Articles.” Note that the field names are slightly different and that two new fields have been added (WhitePaper and BlackInk) to describe the reflective characteristics of the page from which the image was acquired.

If the Source can provide TWPT_CIEXYZ, it must support all operations on this structure.

Field Descriptions

ColorSpace Defines the original color space that was transformed into CIE XYZ. Use a constant of type TWPT_xxxx. This value is not set-able by the application. Application should write TWON_DONTCARE16 into this on a MSG_SET.

LowEndian Used to indicate which data byte is taken first. If zero, then high byte is first. If non-zero, then low byte is first.

DeviceDependent If non-zero then color data is device-dependent and only ColorSpace is valid in this structure.

VersionNumber Version of the color space descriptor specification used to define the transform data. The current version is zero.


StageABC Describes parametrics for the first stage transformation of the Postscript Level 2 CIE color space transform process.

StageLMN Describes parametrics for the first stage transformation of the Postscript Level 2 CIE color space transform process.

WhitePoint Values that specify the CIE 1931 (XYZ space) tri-stimulus value of the diffused white point.

BlackPoint Values that specify the CIE 1931 (XYZ space) tri-stimulus value of the diffused black point.

WhitePaper Values that specify the CIE 1931 (XYZ space) tri-stimulus value of ink-less “paper” from which the image was acquired.

BlackInk Values that specify the CIE 1931 (XYZ space) tri-stimulus value of solid black ink on the “paper” from which the image was acquired.

Samples[1] Optional table look-up values used by the decode function. Samples are ordered sequentially and end-to-end as A, B, C, L, M, and N.


Chapter 8

TW_CIEPOINTtypedef struct { TW_FIX32 X; TW_FIX32 Y; TW_FIX32 Z;} TW_CIEPOINT, FAR * pTW_CIEPOINT;

Used by

Embedded in the TW_CIECOLOR structure

Description

Defines a CIE XYZ space tri-stimulus value. This structure parallels the TCIEPoint structure definition in Appendix A, "TWAIN Articles.”

Field Descriptions

X First tri-stimulus value of the CIE space representation.

Y Second tri-stimulus value of the CIE space representation.

Z Third tri-stimulus value of the CIE space representation.


TW_CUSTOMDSDATAtypedef struct { TW_UINT32 InfoLength;/* Length (in bytes) of data */ TW_HANDLE hData; /* Handle to data */} TW_CUSTOMDSDATA, FAR * pTW_CUSTOMDSDATA;

Used by

DG_CONTROL / DAT_CUSTOMDSDATA / MSG_GETDG_CONTROL / DAT_CUSTOMDSDATA / MSG_SET

Description

Allows for a data source and application to pass custom data to each other.

The format of the data contained in InfoData will be data source specific and will not be defined by the TWAIN API. This structure will be used by an application to query the data source for its current settings, and to archive them to disk. Although the format for this custom data is not defined by TWAIN, source implementers are encouraged to use a ASCII representation for the custom data to be used for settings archival. A Windows INI style format would be easy to implement and allow for additional features to be added without breaking backwards compatibility.

It is also recommended that source vendors embed basic source revision and vendor ID information in the InfoData body so they can determine if the structure being based to the data source is correct.

Note: 1.x versions of the specification have shown the following structure.

typedef struct { TW_UINT32 InfoLength; /* Length (in bytes) of data */ TW_UINT8 InfoData[1]; /* Array (Length) bytes long */} TW_CUSTOMDSDATA, FAR * pTW_CUSTOMDSDATA;

Starting with TWAIN 2.0 only the structure with hData is considered correct. If both a driver and an application are reporting version 2 by examining the TW_IDENTITY.SupportedGroups for DF_APP2 and DF_DS2, then both may assume that hData is in use. It is not sufficient to check the TW_IDENTITY. ProtocolMajor field for a value greater than or equal to 2.

For older drivers and applications it’s expected that most developers have followed the use of hData from the TWAIN.H file, however, good defensive programming recommends at least attempting to anticipate both forms. On Window systems the developer can use GlobalSize() to test if the TW_CUSTOMDSDATA structure is greater than sizeof(TW_CUSTOMDSDATA), which would suggest that hData isn’t a pointer, but is the actual beginning of the data. Other calls like GlobalLock() and IsBadReadPtr() can be used to check the validity of the pointer in hData. No system is perfect, but it should be possible to cover most drivers and applications this way.


Chapter 8

Field Descriptions

InfoLength Length, in bytes, of data

hData Handle to memory containing InfoLength bytes of data


TW_DECODEFUNCTIONtypedef struct { TW_FIX32 StartIn; TW_FIX32 BreakIn; TW_FIX32 EndIn; TW_FIX32 StartOut; TW_FIX32 BreakOut; TW_FIX32 EndOut; TW_FIX32 Gamma; TW_FIX32 SampleCount;} TW_DECODEFUNCTION, FAR * pTW_DECODEFUNCTION;

Used by

Embedded in the TW_TRANSFORMSTAGE structure that is embedded in the TW_CIECOLOR structure

Description

Defines the parameters used for channel-specific transformation. The transform can be described either as an extended form of the gamma function or as a table look-up with linear interpolation. This structure parallels the TDecodeFunction structure definition in Appendix A, "TWAIN Articles.”

Field Descriptions

StartIn Starting input value of the extended gamma function. Defines the minimum input value of channel data.

BreakIn Ending input value of the extended gamma function. Defines the maximum input value of channel data.

EndIn The input value at which the transform switches from linear transformation/interpolation to gamma transformation.

StartOut Starting output value of the extended gamma function. Defines the minimum output value of channel data.

BreakOut Ending output value of the extended gamma function. Defines the maximum output value of channel data.

EndOut The output value at which the transform switches from linear transformation/interpolation to gamma transformation.

Gamma Constant value. The exponential used in the gamma function.

SampleCount The number of samples in the look-up table. Includes the values of StartIn and EndIn. Zero-based index (actually, number of samples - 1). If zero, use extended gamma, otherwise use table look-up.


Chapter 8


TW_DEVICEEVENTtypedef struct { TW_UINT32 Event; TW_STR255 DeviceName; TW_UINT32 BatteryMinutes; // Battery Minutes Remaining TW_INT16 BatteryPercentage; // Battery Percentage Remaining TW_INT32 PowerSupply; // Power Supply TW_FIX32 XResolution; // Resolution TW_FIX32 YResolution; // Resolution TW_UINT32 FlashUsed2; // Flash Used2 TW_UINT32 AutomaticCapture; // Automatic Capture TW_UINT32 TimeBeforeFirstCapture; // Automatic Capture TW_UINT32 TimeBetweenCaptures; // Automatic Capture} TW_DEVICEEVENT, FAR * pTW_DEVICEEVENT;

Used by


Description

Provides information about the Event that was raised by the Source. The Source should only fill in those fields applicable to the Event. The Application must only read those fields applicable to the Event.

Field Descriptions

Event One of the TWDE_xxxx values. Defines event that has taken place.

DeviceName The name of the device that generated the event.

Valid for TWDE_BATTERYCHECK only

BatteryMinutes Minutes of battery power remaining.

BatteryPercentage Percentage of battery power remaining.

Valid for TWDE_POWERSUPPLY only

PowerSupply Current power supply in use.

Valid for TWDE_RESOLUTION only

XResolution Current X Resolution.

YResolution Current Y Resolution.

Valid for TWDE_FLASHUSED2 only

FlashUsed2 Current flash setting.

Valid for TWDE_AUTOMATICCAPTURE only


Chapter 8

AutomaticCapture Number of images camera will capture.

TimeBeforeFirstCapture Number of seconds before first capture.

TimeBetweenCaptures Hundredths of a second between captures.


TW_ENTRYPOINT typedef struct {

TW_UINT32 Size; DSM_ENTRY DSM_Entry; DSM_MEMALLOCATE DSM_MemAllocate; DSM_MEMFREE DSM_MemFree; DSM_MEMLOCK DSM_MemLock; DSM_MEMUNLOCK DSM_MemUnlock;

} TW_ENTRYPOINT, FAR * pTW_ENTRYPOINT;

Used byDG_CONTROL / DAT_ENTRYPOINT / MSG_GET DG_CONTROL / DAT_ENTRYPOINT / MSG_SET

Description

Provides entry points required by TWAIN 2.0 Applications and Sources.

Field Descriptions Size Size of the structure in bytes. The application must set this

before calling MSG_GET. The Source should examine this when processing a MSG_SET.

DSM_Entry A pointer to the DSM_Entry function. TWAIN 2.0 Sources must use this value instead of getting it themselves.

DSM_MemAllocate A pointer to the memory allocation function, taking the form

TW_HANDLE PASCAL DSM_MemAllocate (TW_UINT32).

DSM_MemFree A pointer to the memory free function, taking the form

void PASCAL DSM_MemAllocate (TW_HANDLE)

DSM_MemLock A pointer to the memory lock function, taking the form

TW_MEMREF PASCAL DSM_MemAllocate (TW_HANDLE)

DSM_MemUnlock A pointer to the memory unlock function, taking the form void PASCAL DSM_MemUnlock (TW_HANDLE)


Chapter 8

TW_ELEMENT8typedef struct { TW_UINT8 Index; TW_UINT8 Channel1; TW_UINT8 Channel2; TW_UINT8 Channel3; } TW_ELEMENT8, FAR * pTW_ELEMENT8;

Used by

Embedded in the TW_GRAYRESPONSE, TW_PALETTE8 and TW_RGBRESPONSE structures

Description

This structure holds the tri-stimulus color palette information for TW_PALETTE8 structures. The order of the channels shall match their alphabetic representation. That is, for RGB data, R shall be channel 1. For CMY data, C shall be channel 1. This allows the application and Source to maintain consistency. Grayscale data will have the same values entered in all three channels.

Field Descriptions

Index Value used to index into the color table. Especially useful on the Macintosh.

Channel1 First tri-stimulus value (e.g. Red).

Channel2 Second tri-stimulus value (e.g. Green).

Channel3 Third tri-stimulus value (e.g. Blue).


TW_ENUMERATION typedef struct { TW_UINT16 ItemType; TW_UINT32 NumItems; TW_UINT32 CurrentIndex; TW_UINT32 DefaultIndex; TW_UINT8 ItemList[1]; } TW_ENUMERATION, FAR * pTW_ENUMERATION;

Used by

TW_CAPABILITY structure (when ConType field specifies TWON_ENUMERATION)

Description

Stores a group of individual values describing a capability. The values are ordered from lowest to highest values, but the step size between each value is probably not uniform. Such a list would be useful to describe the discreet resolutions of a capture device supporting, say, 75, 150, 300, 400, and 800 dots per inch.

This structure is related in function and purpose to TW_ARRAY, TW_ONEVALUE, and TW_RANGE.

Field Descriptions

ItemType The type of items in the enumerated list. The type is indicated by the constant held in this field. The constant is of the kind TWTY_xxxx. All items in the array have the same size.

NumItems How many items are in the enumeration.

CurrentIndex The item number, or index (zero-based) into ItemList[], of the “current” value for the capability.

DefaultIndex The item number, or index (zero-based) into ItemList[], of the “power-on” value for the capability.

ItemList[1] The enumerated list: one value resides within each array element. Space for the list is not allocated inside this structure. The ItemList value is simply a placeholder for the start of the actual array, which must be allocated when the container is allocated. Remember to typecast the allocation to ItemType, as well as references to the elements of the array.

Ex:Second element of ICAP_XFERMECH (assuming >= 2 NumItems)value = ((TW_UINT16*)twenum.ItemList)[1];


Chapter 8

TW_EVENTtypedef struct { TW_MEMREF pEvent; TW_UINT16 TWMessage;} TW_EVENT, FAR * pTW_EVENT;

Used byDG_CONTROL / DAT_EVENT / MSG_PROCESSEVENT

Description

Used to pass application events/messages from the application to the Source. The Source is responsible for examining the event/message, deciding if it belongs to the Source, and returning an appropriate return code to indicate whether or not the Source owns the event/message. This process is covered in more detail in the Event Loop section of Chapter 3, "Application Implementation.”

Field Descriptions

pEvent A pointer to the event/message to be examined by the Source.Under Microsoft Windows, pEvent is a pMSG (pointer to a Microsoft Windows MSG struct). That is, the message the application received from GetMessage().On the Macintosh, pEvent is a pointer to an EventRecord.

TWMessage Any message (MSG_xxxx) the Source needs to send to the application in response to processing the event/message. The messages currently defined for this purpose are MSG_NULL, MSG_XFERREADY and MSG_CLOSEDSREQ.


TW_EXTIMAGEINFOtypedef struct { TW_UINT32 NumInfos; TW_INFO Info[1];} TW_EXTIMAGEINFO, FAR * pTW_EXTIMAGEINFO;

Used by

DG_IMAGE / DAT_EXTIMAGEINFO / MSG_GET

Description

This structure is used to pass extended image information from the data source to application at the end of State 7. The application creates this structure at the end of State 7, when it receives XFERDONE. Application fills NumInfos for Number information it needs, and array of extended information attributes in Info[ ] array. Application, then, sends it down to the source using the above operation triplet. The data source then examines each Info, and fills the rest of data with information allocating memory when necessary.

The design of extended image information allows for two methods of passing multiple InfoID types. For instance, assume it is possible for a Source to generate more than one barcode off an image. An Application can request to acquire the data in one of two ways. The first way is as follows:

Applications asks for:

TW_EXTIMAGEINFO

NumInfos = 4

TW_INFO[0]

InfoID = TWEI_BARCODECOUNT

ItemType = TW_UNINT32

NumItems = 0

CondCode = 0 Item = 0

TW_INFO[1]

InfoID = TWEI_BARCODETYPE


NumItems = 0


TW_INFO[2]

InfoID = TWEI_BARCODETEXTLENGTH


NumItems = 0



Chapter 8

TW_INFO[3]

InfoID = TWEI_BARCODETEXT

ItemType = 0

NumItems = 0


The Source returns…

TW_EXTIMAGEINFO

NumInfos = 4

TW_INFO[0]


ItemType = TW_UINT32

NumItems = 1

CondCode = TWCC_SUCCESS

Item = 2

TW_INFO[1]



NumItems = 2


Item = TW_HANDLE-0

TW_INFO[2]



NumItems = 2


Item = TW_HANDLE-1

TW_INFO[3]


ItemType = TW_HANDLE

NumItems = 2


Item = TW_HANDLE-2

((TW_UINT32*)TW_HANDLE-0)[0] TWBT_3OF9

((TW_UINT32*)TW_HANDLE-0)[1] TWBT_2OF5INTERLEAVED

((TW_UINT32*)TW_HANDLE-1)[0] 16



((TW_UINT8*)TW_HANDLE-2)[0] Barcode Text 0

((TW_UINT8*)TW_HANDLE-2)[ ((TW_UINT32*)TW_HANDLE-1)[0]]

Barcode Text 1

Note that Item is a pointer to the first datum for this TW_INFO. The Item field must be a TW_HANDLE to the data if the value if the following is true:

(SizeOfSpecifiedItem * NumItems) > sizeof(TW_HANDLE)

It is the responsibility of the Application to free both the TW_EXTIMAGEINFO structure and any Item values that are TW_HANDLE, based on this calculation.The reason for this design is so that the Source and Application can easily index through the TW_INFO structures (ex: TW_EXTIMAGEINFO->Item[0])Note that the above structure could also be requested by the Application as follows:TW_EXTIMAGEINFO

NumInfos = 5

TW_INFO[0]



NumItems = 0

CondCode = 0

Item = 0

TW_INFO[1]



NumItems = 0

CondCode = 0

Item = 0

TW_INFO[2]



NumItems = 0

CondCode = 0

Item = 0

TW_INFO[3]


ItemType = 0

NumItems = 0

CondCode = 0


Chapter 8

Item = 0

TW_INFO[4]


ItemType = 0

NumItems = 0

CondCode = 0

Item = 0

If the Source detects multiple occurrences of a tag, then it must distribute the data as best it can across the applicable TW_INFO fields. NumItems must be equal to one, and if there are not enough TW_INFOs supplied for the specified InfoID, then any remaining data is discarded by the Source. In this instance the return structure is big enough, and would look like the following…

TW_EXTIMAGEINFO

NumInfos = 5

TW_INFO[0]



NumItems = 1


Item = 2

TW_INFO[1]



NumItems = 2


Item = TW_HANDLE-0

TW_INFO[2]



NumItems = 2


Item = TW_HANDLE-1

TW_INFO[3]



NumItems = 1



Item = TW_HANDLE-2

TW_INFO[4]



NumItems = 1


Item = TW_HANDLE-3

((TW_UINT32*)TW_HANDLE-0)[0] TWBT_3OF9

((TW_UINT32*)TW_HANDLE-0)[1] TWBT_2OF5INTERLEAVED



((TW_UINT8*)TW_HANDLE-2)[0] Barcode Text 0

((TW_UINT8*)TW_HANDLE-3)[ 0] Barcode Text 1

Field Descriptions

NumInfos Number of information that application is requesting. This is filled by the application. If positive, then the application is requesting specific extended image information. The application should allocate memory and fill in the attribute tag for image information.

Info[1] Array of information. See TW_INFO structure.


Chapter 8

TW_FILESYSTEMtypedef struct { // DG_CONTROL / DAT_FILESYSTEM / MSG_xxxx fields… TW_STR255 InputName; TW_STR255 OutputName; TW_MEMREF Context; // DG_CONTROL / DAT_FILESYSTEM / MSG_COPY // DG_CONTROL / DAT_FILESYSTEM / MSG_DELETE field… int Recursive; // DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFO fields… TW_INT32 FileType; TW_UINT32 Size; TW_STR32 CreateTimeDate; TW_STR32 ModifiedTimeDate; TW_UINT32 FreeSpace; TW_INT32 NewImageSize; TW_UINT32 NumberOfFiles; TW_UINT32 NumberOfSnippets; TW_UINT32 DeviceGroupMask; char Reserved[508];} TW_FILESYSTEM, FAR * pTW_FILESYSTEM;

Used byDG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_COPYDG_CONTROL / DAT_FILESYSTEM / MSG_CREATEDIRECTORYDG_CONTROL / DAT_FILESYSTEM / MSG_DELETEDG_CONTROL / DAT_FILESYSTEM / MSG_FORMATMEDIADG_CONTROL / DAT_FILESYSTEM / MSG_GETCLOSEDG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_GETINFODG_CONTROL / DAT_FILESYSTEM / MSG_GETNEXTFILEDG_CONTROL / DAT_FILESYSTEM / MSG_RENAME

Description

Provides information about the currently selected device.


Field Descriptions

InputName The name of the input or source file.

OutputName The result of an operation or the name of a destination file.

Context A pointer to Source specific data used to remember state information, such as the current directory.

MSG_GETINFO / MSG_GETFILEFIRST / MSG_DELETE

Recursive When set to TRUE recursively apply the operation. (ex: deletes all subdirectories in the directory being deleted; or copies all sub-directories in the directory being copied.

MSG_GETINFO / MSG_GETFILEFIRST / MSG_GETFILENEXT

FileType One of the TWFY_xxxx values.

Size TWFY_DIRECTORY- Total size of media in bytes.TWFY_IMAGE- Size of image in bytes.TWFY_xxxx- All other file types return a value of 0.

CreateTimeDate The create date of the file, in the form “YYYY/MM/DD HH:mm:SS:sss” where YYYY is the year, MM is the numerical month, DD is the numerical day, HH is the hour, mm is the minute, SS is the second, and sss is the millisecond.

ModifyTimeDate Last date the file was modified. Same format as CreateTimeDate.

FreeSpace The bytes of free space left on the current device.

NewImageSize An estimate of the amount of space a new image would take up, based on image layout, resolution and compression. Dividing this value into the FreeSpace will yield the approximate number of images that the Device has room for.

NumberOfFiles TWFY_IMAGE- Return 0TWFY_xxxx- Return number of TWFY_IMAGE files on the file system including those in all sub-directories.

NumberOfSnippets The number of audio snippets associated with a file of type TWFY_IMAGE.

DeviceGroupMask A set of bits, with each bit uniquely identifying a device of type TWFY_CAMERA and any associated TWFY_CAMERATOP and/or TWFY_CAMERABOTTOM devices. See “File System” on pageA-11 of this specification for more information.

Reserved Space reserved for future expansion of this structure.


Chapter 8

TW_FIX32typedef struct { TW_INT16 Whole; TW_UINT16 Frac;} TW_FIX32, FAR * pTW_FIX32;

Used by

Embedded in the TW_CIECOLOR, TW_CIEPOINT, TW_DECODEFUNCTION, TW_FRAME, TW_IMAGEINFO, and TW_TRANSFORMSTAGE structures.

Used in TW_ARRAY, TW_ENUMERATION, TW_ONEVALUE, and TW_RANGE structures when ItemType is TWTY_FIX32.

Description

Stores a Fixed point number in two parts, a whole and a fractional part. The Whole part carries the sign for the number. The Fractional part is unsigned.

Field Descriptions

The following functions convert TW_FIX32 to float and float to TW_FIX32:

/**********************************************************

* FloatToFix32

* Convert a floating point value into a FIX32.**********************************************************/TW_FIX32 FloatToFix32 (float floater){ TW_FIX32 Fix32_value; TW_INT32 value = (TW_INT32) (floater * 65536.0 + 0.5); Fix32_value.Whole = value >> 16; Fix32_value.Frac = value & 0x0000ffffL; return (Fix32_value);}/*********************************************************** Fix32ToFloat* Convert a FIX32 value into a floating point value.**********************************************************/float FIX32ToFloat (TW_FIX32 fix32){ float floater; floater = (float) fix32.Whole + (float) fix32.Frac / 65536.0; return floater;}

Whole The Whole part of the floating point number. This number is signed.

Frac The Fractional part of the floating point number. This number is unsigned.


TW_FRAMEtypedef struct { TW_FIX32 Left; TW_FIX32 Top; TW_FIX32 Right; TW_FIX32 Bottom;} TW_FRAME, FAR * pTW_FRAME;

Used by

Embedded in the TW_IMAGELAYOUT structure

Description

Defines a frame rectangle in ICAP_UNITS coordinates.

Field Descriptions

Left Value of the left-most edge of the rectangle (in ICAP_UNITS).

Top Value of the top-most edge of the rectangle (in ICAP_UNITS).

Right Value of the right-most edge of the rectangle (in ICAP_UNITS).

Bottom Value of the bottom-most edge of the rectangle (in ICAP_UNITS).


Chapter 8

TW_GRAYRESPONSEtypedef struct { TW_ELEMENT8 Response[1];} TW_GRAYRESPONSE, FAR * pTW_GRAYRESPONSE;

Used byDG_IMAGE / DAT_GRAYRESPONSE / MSG_RESETDG_IMAGE / DAT_GRAYRESPONSE / MSG_SET

Description

This structure is used by the application to specify a set of mapping values to be applied to grayscale data. Use this structure for grayscale data whose bit depth is up to and including 8-bits. This structure can only be used if TW_IMAGEINFO. PixelType is TWPT_GRAY. The number of elements in the array is determined by TW_IMAGEINFO.BitsPerPixel—the number of elements is 2 raised to the power of TW_IMAGEINFO.BitsPerPixel.

This structure is primarily intended for use by applications that bypass the Source’s built-in user interface.

Field Descriptions

Response[1] Transfer curve descriptors. All three channels (Channel1, Channel2 and Channel3) must contain the same value for every entry.


TW_HANDLE

See “Platform Specific Typedefs” on page 8-4.for information on the actual mapping of this type.

Used by

Embedded in the TW_CAPABILITY and TW_USERINTERFACE structures

Description

The typedef of Handles are defined by the operating system. TWAIN defines TW_HANDLE to be the handle type supported by the operating system.

Field Descriptions

See definitions above


Chapter 8

TW_IDENTITYtypedef struct { TW_UINT32 Id; TW_VERSION Version; TW_UINT16 ProtocolMajor; TW_UINT16 ProtocolMinor; TW_UINT32 SupportedGroups; TW_STR32 Manufacturer; TW_STR32 ProductFamily; TW_STR32 ProductName;} TW_IDENTITY, FAR * pTW_IDENTITY;

Used by

A large number of the operations because it identifies the application and the Source

Description

Provides identification information about a TWAIN entity. Used to maintain consistent communication between entities.

Field Descriptions

Id A unique, internal identifier for the TWAIN entity. This field is only filled by the Source Manager. Neither an application nor a Source should fill this field. The Source uses the contents of this field to “identify” which application is invoking the operation sent to the Source.

Version A TW_VERSION structure identifying the TWAIN entity.

ProtocolMajor Major number of latest TWAIN version that this element supports (see TWON_PROTOCOLMAJOR).

ProtocolMinor Minor number of latest TWAIN version that this element supports (see TWON_PROTOCOLMINOR).


SupportedGroups •^:The application will normally set this field to specify which Data Group(s) it wants the Source Manager to sort Sources by when presenting the Select Source dialog, or returning a list of available Sources. The application sets this prior to invoking a MSG_USERSELECT operation.

•^:The application may also set this field to specify which Data Group(s) it wants the Source to be able to acquire and transfer. The application must do this prior to sending the Source its MSG_ENABLEDS operation.

•^:The Source must set this field to specify which Data Group(s) it can acquire. It will do this in response to a MSG_OPENDS.

•^:Beginning with TWAIN 2.0 the Source Manager reserves the most significant two byes in the SupportedGroups for the Data Flags (0x0001000 to 0xFFFF0000).

DF_DSM2 – identifies the Source Manager as TWAIN 2.0 compliant

DF_APP2 – is set by an Application that is TWAIN 2.0 compliant

DF_DS2 – is set by a Source that is TWAIN 2.0 compliant Manufacturer String identifying the manufacturer of the application or Source. e.g.

“Aldus”.

ProductFamily Tells an application that performs device-specific operations which product family the Source supports. This is useful when a new Source has been released and the application doesn’t know about the particular Source but still wants to perform Custom operations with it. e.g. “ScanMan”.

ProductName A string uniquely identifying the Source. This is the string that will be displayed to the user at Source select-time. This string must uniquely identify your Source for the user, and should identify the application unambiguously for Sources that care. e.g. “ScanJet IIc”.


Chapter 8

TW_IMAGEINFOtypedef struct { TW_FIX32 XResolution; TW_FIX32 YResolution; TW_INT32 ImageWidth; TW_INT32 ImageLength; TW_INT16 SamplesPerPixel; TW_INT16 BitsPerSample[8]; TW_INT16 BitsPerPixel; TW_BOOL Planar; TW_INT16 PixelType; TW_UINT16 Compression;} TW_IMAGEINFO, FAR * pTW_IMAGEINFO;

Used by

The DG_IMAGE / DAT_IMAGEINFO / MSG_GET operation

Description

Describes the “real” image data, that is, the complete image being transferred between the Source and application. The Source may transfer the data in a different format--the information may be transferred in “strips” or “tiles” in either compressed or uncompressed form. See the TW_IMAGEMEMXFER structure for more information.

The term “sample” is referred to a number of times in this structure. It holds the same meaning as in the TIFF specification. A sample is a contiguous body of image data that can be categorized by the channel or “ink color” it was captured to describe. In an R-G-B (Red-Green-Blue) image, such as on your TV or computer’s CRT, each color channel is composed of a specific color. There are 3 samples in an R-G-B; Red, Green, and Blue. A C-Y-M-K image has 4 samples. A Grayscale or Black and White image has a single sample.

Note: he value -1 in ImageWidth and ImageLength are special cases. It is possible for a Source to not know either its Width or Length. Applications need to consider this when allocating memory or otherwise dealing with the size of the Image.

Field Descriptions

XResolution The number of pixels per ICAP_UNITS in the horizontal direction. The current unit is assumed to be “inches” unless it has been otherwise negotiated between the application and Source.

YResolution The number of pixels per ICAP_UNITS in the vertical direction.

ImageWidth How wide, in pixels, the entire image to be transferred is. If the Source doesn’t know, set this field to -1 (hand scanners may do this).--1 can only be used if the application has set ICAP_UNDEFINEDIMAGESIZE to TRUE.


ImageLength How tall/long, in pixels, the image to be transferred is. If the Source doesn’t know, set this field to -1 (hand scanners may do this).-1 can only be used if the application has set ICAP_UNDEFINEDIMAGESIZE to TRUE.

SamplesPerPixel The number of samples being returned. For R-G-B, this field would be set to 3. For C-M-Y-K, 4. For Grayscale or Black and White, 1.

BitsPerSample[8] For each sample, the number of bits of information. 24-bit R-G-B will typically have 8 bits of information in each sample (8+8+8). Some 8-bit color is sampled at 3 bits Red, 3 bits Green, and 2 bits Blue. Such a scheme would put 3, 3, and 2 into the first 3 elements of this array. The supplied array allows up to 8 samples. Samples are not limited to 8 bits. However, both the application and Source must simultaneously support sample sizes greater than 8 bits per color.

BitsPerPixel The number of bits in each image pixel (or bit depth). This value is invariant across the image. 24-bit R-G-B has BitsPerPixel = 24. 40-bit C-M-Y-K has BitsPerPixel=40. 8-bit Grayscale has BitsPerPixel = 8. Black and White has BitsPerPixel = 1.

Planar If SamplesPerPixel > 1, indicates whether the samples follow one another on a pixel-by-pixel basis (R-G-B-R-G-B-R-G-B...) as is common with a one-pass scanner or all the pixels for each sample are grouped together (complete group of R, complete group of G, complete group of B) as is common with a three-pass scanner. If the pixel-by-pixel method (also known as “chunky”) is used, the Source should set Planar = FALSE. If the grouped method (also called “planar”) is used, the Source should set Planar = TRUE.

PixelType This is the highest categorization for how the data being transferred should be interpreted by the application. This is how the application can tell if the data is Black and White, Grayscale, or Color. Currently, the only color type defined is “tri-stimulus”, or color described by three characteristics. Most popular color description methods use tri-stimulus descriptors. For simplicity, the constant used to identify tri-stimulus color is called TWPT_RBG, for R-G-B color. There is no default for this value. Fill this field with the appropriate TWPT_xxxx constant.

Compression The compression method used to process the data being transferred. Default is no compression. Fill this field with the appropriate TWCP_xxxx constant.


Chapter 8

TW_IMAGELAYOUTtypedef struct { TW_FRAME Frame; TW_UINT32 DocumentNumber; TW_UINT32 PageNumber; TW_UINT32 FrameNumber;} TW_IMAGELAYOUT, FAR * pTW_IMAGELAYOUT;

Used byDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDG_IMAGE / DAT_IMAGELAYOUT / MSG_GETDEFAULTDG_IMAGE / DAT_IMAGELAYOUT / MSG_RESETDG_IMAGE / DAT_IMAGELAYOUT / MSG_SET

Description

Involves information about the original size of the acquired image and its position on the original “page” relative to the “page’s” upper-left corner. Default measurements are in inches (units of measure can be changed by negotiating the ICAP_UNITS capability). This information may be used by the application to relate the acquired (and perhaps processed image) to the original. Further, the application can, using this structure, set the size of the image it wants acquired.

Another attribute of this structure is the included frame, page, and document indexing information. Most Sources and applications, at least at first, will likely set all these fields to one. For Sources that can acquire more than one frame from a page in a single acquisition, the FrameNumber field will be handy. Sources that can acquire more than one page from a document feeder will use PageNumber and DocumentNumber. These fields will be especially useful for forms-processing applications and other applications with similar document tracking requirements.

Field Descriptions

Frame Defines the Left, Top, Right, and Bottom coordinates (in ICAP_UNITS) of the rectangle enclosing the original image on the original “page”. If the application isn’t interested in setting the origin of the image, set both Top and Left to zero. The Source will fill in the actual values following the acquisition. See also TW_FRAME.

DocumentNumber The document number, assigned by the Source, that the acquired data originated on. Useful for grouping pages together. Usually a physical representation, this could just as well be a logical construct. Initial value is 1. Increment when a new document is placed into the document feeder (usually tell this has happened when the feeder empties). Reset when no longer acquiring from the feeder.

PageNumber The page which the acquired data was captured from. Useful for grouping Frames together that are in some way related, usually Source. Usually a physical representation, this could just as well be a logical construct. Initial value is 1. Increment for each page fed from a page feeder. Reset when a new document is placed into the feeder.


FrameNumber Usually a chronological index of the acquired frame. These frames are related to one another in some way; usually they were acquired from the same page. The Source assigns these values. Initial value is 1. Reset when a new page is acquired from.


Chapter 8

TW_IMAGEMEMXFERtypedef struct {

TW_UINT16 Compression; TW_UINT32 BytesPerRow; TW_UINT32 Columns; TW_UINT32 Rows; TW_UINT32 XOffset; TW_UINT32 YOffset; TW_UINT32 BytesWritten; TW_MEMORY Memory;

} TW_IMAGEMEMXFER, FAR * pTW_IMAGEMEMXFER;

Used by


Description

Describes the form of the acquired data being passed from the Source to the application. When used in combination with a TW_IMAGEINFO structure, the application can correctly interpret the image.

This structure allows transfer of “chunks” from the acquired data. These portions may be either “strips” or “tiles.” Strips are tiles whose width matches that of the full image. Strips are always passed sequentially, from “top” to “bottom”. A tile’s position does not necessarily follow that of the previously passed tile. Most Sources will transfer strips.

Note: The application should remember what corner was contained in the first tile of a plane. When the opposite corner is delivered, the plane is complete. The dimensions of the memory transfers may vary.

Data may be passed either compressed or uncompressed. All Sources must pass uncompressed data. Sources are not required to support compressed data transfers. Compressed data transfers, and how the values are entered into the fields of this structure, are described in Chapter 4, "Advanced Application Implementation.”

Following is a picture of some of the fields from a TW_IMAGEMEMXFER structure. The large outline shows the entire image which was selected to be transferred. The smaller rectangle shows the particular portion being described by this TW_IMAGEMEMXFER structure.

Note: Remember that for a “strip” transfer XOffset = 0, and Columns = TW_IMAGEINFO.ImageWidth.


Field Descriptions

Compression The compression method used to process the data being transferred. Write the constant (TWCP_xxxx) that precisely describes the type of compression used for the buffer. This may be different from the method reported in the TW_IMAGEINFO structure (if the user selected a different method before the actual transfer began, for instance). This is unlikely, but possible. The application can optionally abort the acquisition if the value in this field differs from the TW_IMAGEINFO value. Default is no compression (TWCP_NONE) and most transfers will probably be uncompressed. See the list of constants in the TWAIN.H file.

BytesPerRow The number of uncompressed bytes in each row of the piece of the image being described in this buffer.

Columns The number of uncompressed columns (in pixels) in this buffer.

Rows The number or uncompressed rows (in pixels) in this buffer.

XOffset How far, in pixels, the left edge of the piece of the image being described by this structure is inset from the “left” side of the original image. If the Source is transferring in “strips”, this value will equal zero. If the Source is transferring in “tiles”, this value will often be non-zero.

YOffset Same idea as XOffset, but the measure is in pixels from the “top” of the original image to the upper edge of this piece.

BytesWritten The number of bytes written into the transfer buffer. This field must always be filled in correctly, whether compressed or uncompressed data is being transferred.

Memory A structure of type TW_MEMORY describing who must dispose of the buffer, the actual size of the buffer, in bytes, and where the buffer is located in memory.


Chapter 8

TW_INFOtypedef struct { TW_UINT16 InfoID; TW_UINT16 ItemType; TW_UINT16 NumItems; TW_UINT16 CondCode; TW_UINTPTR Item; } TW_INFO, FAR * pTW_INFO;

Used by

Within TW_EXTIMAGEINFO structure.

Description

This structure is used to pass specific information between the data source and the application.

Field Descriptions

InfoID Tag identifying an information. For TW_EXTIMAGEINFO, the information ID is defined as IACAP_xxxx. (Please refer to Extended Image capabilities).

ItemType Item data type. It is one of TWTY_xxxx value as listed in the TW_INFO.ITEMTYPE below.

NumItems Number of items for this field.

CondCode This is condition code of availability of data for extended image attribute requested. Following is the list of possible condition codes:TWRC_INFONOTSUPPORTED

TWRC_DATANOTAVAILABLE

Item The TW_INFO.Item field contains either data or a handle to data. The field contains data if the total amount of data is less than or equal to four bytes. The field contains a handle of the total amount of data is more than four bytes. The amount of data is determined by multiplying TW_INFO.NumItems times the byte size of the data type specified by TW_INFO.ItemType.If the TW_INFO.Item field contains a handle to data, then the Application is responsible for freeing that memory.


TW_INFO.ITEMTYPE

TW_INFO Return Codes

Following is the list of added return codes.

ItemType NumItems Data/Pointer Reason

TW_STR32 1 handle to data (sizeof (TW_STR32) * 1) > 4

TW_INT32 1 data (sizeof (TW_INT32) * 1) == 4

TW_INT8 3 data (sizeof (TW_INT8) * 3) < 4

TW_INT8 5 handle to data (sizeof (TW_INT8) * 5) > 4

TWRC_INFONOTSUPPORTED Requested information is not supported.

TWRC_DATANOTAVAILABLE Requested information is supported, but some unknown reason, information is not available.


Chapter 8

TW_JPEGCOMPRESSIONtypedef struct { TW_UINT16 ColorSpace; TW_UINT32 SubSampling; TW_UINT16 NumComponents; TW_UINT16 RestartFrequency; TW_UINT16 QuantMap[4]; TW_MEMORY QuantTable[4]; TW_UINT16 HuffmanMap[4]; TW_MEMORY HuffmanDC[2]; TW_MEMORY HuffmanAC[2];} TW_JPEGCOMPRESSION, FAR * pTW_JPEGCOMPRESSION;

Used byDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_GETDEFAULTDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_RESETDG_IMAGE / DAT_JPEGCOMPRESSION / MSG_SET

Description

Describes the information necessary to transfer a JPEG-compressed image during a buffered transfer. Images compressed in this fashion will be compatible with the JPEG File Interchange Format, version 1.1. For more information on JPEG and TWAIN, see Chapter 4, "Advanced Application Implementation.” The TWAIN JPEG implementation is based on the JPEG Draft International Standard, version 10918-1. The sample tables found in Section K of the JPEG Draft International Standard, version 10918-1 are used as the default tables for QuantTable, HuffmanDC, and HuffmanAC.

Field Descriptions

ColorSpace One of the TWPT_xxxx values. Defines the color space in which the compressed components are stored. Only spaces supported by the Source for ICAP_JPEGPIXELTYPE are valid.

SubSampling Encodes the horizontal and vertical subsampling in the form ABCDEFGH, where ABCD are the high-order four nibbles which represent the horizontal subsampling and EFGH are the low-order four nibbles which represent the vertical subsampling. Each nibble may have a value of 0, 1, 2, 3, or 4. However, max(A,B,C,D) * max(E,F,G,H) must be less than or equal to 10. Subsampling is irrelevant for single component images. Therefore, the corresponding nibbles should be set to 1. e.g. To indicate subsampling two Y for each U and V in a YUV space image, where the same subsampling occurs in both horizontal and vertical axes, this field would hold 0x21102110. For a grayscale image, this field would hold 0x10001000. A CMYK image could hold 0x11111111.

NumComponents Number of color components in the image to be compressed.


RestartFrequency

Number of MDUs (Minimum Data Units) between restart markers. Default is 0, indicating that no restart markers are used. An MDU is defined for interleaved data (i.e. R-G-B, Y-U-V, etc.) as a minimum complete set of 8x8 component blocks.

QuantMap[4] Mapping of components to Quantization tables.

QuantTable[4] Quantization tables.

HuffmanMap[4] Mapping of components to Huffman tables. Null entries signify selection of the default tables.

HuffmanDC[2] DC Huffman tables. Null entries signify selection of the default tables.

HuffmanAC[2] AC Huffman tables. Null entries signify selection of the default tables.


Chapter 8

TW_MEMORYtypedef struct { TW_UINT32 Flags; TW_UINT32 Length; TW_MEMREF TheMem;} TW_MEMORY, FAR * pTW_MEMORY;

Used by

Embedded in the TW_IMAGEMEMXFER and TW_JPEGCOMPRESSION structures

Description

Provides information for managing memory buffers. Memory for transfer buffers is allocated by the application--the Source is asked to fill these buffers. This structure keeps straight which entity is responsible for deallocation.

Field Descriptions

Flags Encodes which entity releases the buffer and how the buffer is referenced. The ownership flags must be used:

• when transferring Buffered Memory data as tiles

• ·when transferring Buffered Memory that is compressed

• in the TW_JPEGCOMPRESSION structureWhen transferring Buffered Memory data as uncompressed strips, the application allocates the buffers and is responsible for setting the ownership flags.This field is used to identify how the memory is to be referenced. The memory is always referenced by a Handle on the Macintosh and a Pointer under UNIX. It is referenced by a Handle or a pointer under Microsoft Windows.Use TWMF_xxxx constants, bit-wise OR’d together to fill this field.

Flag Constants:TWMF_APPOWNS 0x1TWMF_DSMOWNS 0x2TWMF_DSOWNS 0x4TWMF_POINTER 0x8TWMF_HANDLE 0x10

Length The size of the buffer in bytes. Should always be an even number and word-aligned.

TheMem Reference to the buffer. May be a Pointer or a Handle (see Flags field to make this determination). You must typecast this field before referencing it in your code.


TW_MEMREF

See “Platform Specific Typedefs” on page 8-4. for information on the actual mapping of this type.

Used by

Embedded in the TW_EVENT and TW_MEMORY structures

Description

Memory references are specific to each operating system. TWAIN defines TW_MEMREF to be the memory reference type supported by the operating system.

Field Descriptions

See definitions above.


Chapter 8

TW_UINTPTR

On Windows:

typedef UINT_PTR TW_UINTPTR;

On Macintosh and Unix:

//32 bit GNU


//64 bit GNU


Used by

Embedded in the TW_INFO structure.

Description

Integer pointer references are specific to each operating system. TWAIN defines TW_UINTPTR to be the integer pointer reference type supported by the operating system.

Field Descriptions

See definitions above


TW_ONEVALUEtypedef struct { TW_UINT16 ItemType; TW_UINT32 Item;} TW_ONEVALUE, FAR * pTW_ONEVALUE;

Used by

TW_CAPABILITY structure (when ConType field specifies TWON_ONEVALUE)

Description

Stores a single value (item) which describes a capability. This structure is currently used only in a TW_CAPABILITY structure. Such a value would be useful to describe the current value of the device’s contrast, or to set a specific contrast value. This structure is related in function and purpose to TW_ARRAY, TW_ENUMERATION, and TW_RANGE.

Note that in cases where the data type is TW_UINT16, the data should reside in the lower word.

Field Descriptions

ItemType The type of the item. The type is indicated by the constant held in this field. The constant is of the kind TWTY_xxxx.

Item The value.


Chapter 8

TW_PALETTE8typedef struct { TW_UINT16 NumColors; TW_UINT16 PaletteType; TW_ELEMENT8 Colors[256];} TW_PALETTE8, FAR * pTW_PALETTE8;

Used byDG_IMAGE / DAT_PALETTE8 / MSG_GETDG_IMAGE / DAT_PALETTE8 / MSG_GETDEFAULTDG_IMAGE / DAT_PALETTE8 / MSG_RESETDG_IMAGE / DAT_PALETTE8 / MSG_SET

Description

This structure holds the color palette information for buffered memory transfers of type ICAP_PIXELTYPE = TWPT_PALETTE.

Field Descriptions

NumColors Number of colors in the color table; maximum index into the color table should be one less than this (since color table indexes are zero-based).

PaletteType TWPA_xxxx constant specifying the type of palette.

Colors[256] Array of palette values.


TW_PASSTHRUtypedef struct { TW_MEMREF pCommand; TW_UINT32 CommandBytes; TW_INT32 Direction; TW_MEMREF pData; TW_UINT32 DataBytes; TW_UINT32 DataBytesXfered;

} TW_PASSTHRU, FAR * pTW_PASSTHRU;

Used by


Description

Used to bypass the TWAIN protocol when communicating with a device. All memory must be allocated and freed by the Application. Use of this feature is limited to Source writers who require a standard entry point for specialized Applications, such as diagnostics.

Field Descriptions

pCommand Pointer to Command buffer.

CommandBytes Number of bytes in Command buffer.

Direction One of the TWDR_xxxx values. Defines the direction of data flow.

pData Pointer to Data buffer.

DataBytes Number of bytes in Data buffer.

DataBytesXfered Number of bytes successfully transferred.


Chapter 8

TW_PENDINGXFERStypedef struct { TW_UINT16 Count; union { TW_UINT32 EOJ; TW_UINT32 Reserved; };} TW_PENDINGXFERS, FAR *pTW_PENDINGXFERS;

Used by

DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERDG_CONTROL / DAT_PENDINGXFERS / MSG_GETDG_CONTROL / DAT_PENDINGXFERS / MSG_RESET

Description

This structure tells the application how many more complete transfers the Source currently has available. The application should MSG_GET this structure at the conclusion of a transfer to confirm the Source’s current state. If the Source has more transfers pending it will remain in State 6 awaiting initiation of the next transfer by the application.

If it has no more image transfers pending, it will place zero into the Count and will have automatically transitioned to State 5 (audio transfers will remain in State 6, even when the Count goes to zero).

If the Source knows there are more transfers pending but is unsure of the actual number, it should place -1 into Count (for example, with document feeders or continuous video sources). Otherwise, the Source should place the actual number of pending transfers into Count.

Field Descriptions

Count When DAT_XFERGROUP is set to DG_IMAGEThe number of complete transfers a Source has available for the application it is connected to. If no more transfers are available, set to zero. If an unknown and non-zero number of transfers are available, set to -1.When DAT_XFERGROUP is set to DG_AUDIOThe number of complete audio snippet transfers for a given image a Source has available for the application it is connected to. If no more transfers are available, set to zero. –1 is not a valid value.

EOJ The application should check this field if the CAP_JOBCONTROL is set to other than TWJC_NONE. If the EOJ is not 0, the application should expect more data from the driver according to CAP_JOBCONTROL settings.

Reserved Maintained so as not to cause compile time errors for pre-1.7 code.


TW_RANGEtypedef struct { TW_UINT16 ItemType; TW_UINT32 MinValue; TW_UINT32 MaxValue; TW_UINT32 StepSize; TW_UINT32 DefaultValue; TW_UINT32 CurrentValue;} TW_RANGE, FAR * pTW_RANGE;

Used by

TW_CAPABILITY structure (when ConType field specifies TWON_RANGE)

Description

Stores a range of individual values describing a capability. The values are uniformly distributed between a minimum and a maximum value. The step size between each value is constant. Such a value is useful when describing such capabilities as the resolutions of a device which supports discreet, uniform steps between each value, such as 50 through 300 dots per inch in steps of 2 dots per inch (50, 52, 54, ..., 296, 298, 300). This structure is related in function and purpose to TW_ARRAY, TW_ENUMERATION, and TW_ONEVALUE.

Field Descriptions

ItemType The type of items in the list. The type is indicated by the constant held in this field. The constant is of the kind TWTY_xxxx. All items in the list have the same size/type.

MinValue The least positive/most negative value of the range.

MaxValue The most positive/least negative value of the range.

StepSize The delta between two adjacent values of the range. e.g. Item2 - Item1 = StepSize;

DefaultValue The device’s “power-on” value for the capability. If the application is performing a MSG_SET operation and isn’t sure what the default value is, set this field to TWON_DONTCARE32.

CurrentValue The value to which the device (or its user interface) is currently set to for the capability.


Chapter 8

TW_RGBRESPONSEtypedef struct {

ELEMENT8 Response[1];} TW_RGBRESPONSE, FAR * pTW_RGBRESPONSE;

Used by

DG_IMAGE / DAT_RGBRESPONSE / MSG_RESETDG_IMAGE / DAT_RGBRESPONSE / MSG_SET

Description

This structure is used by the application to specify a set of mapping values to be applied to RGB color data. Use this structure for RGB data whose bit depth is up to, and including, 8-bits. The number of elements in the array is determined by TW_IMAGEINFO.BitsPerPixel—the number of elements is 2 raised to the power of TW_IMAGEINFO.BitsPerPixel.

This structure is primarily intended for use by applications that bypass the Source’s built-in user interface.

Field Descriptions

Response[1] Transfer curve descriptors. To minimize color shift problems, writing the same values into each channel is desirable.


TW_SETUPFILEXFERtypedef struct { TW_STR255 FileName; TW_UINT16 Format; TW_INT16 VRefNum;} TW_SETUPFILEXFER, FAR * pTW_SETUPFILEXFER;

Used byDG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDG_CONTROL / DAT_SETUPFILEXFER / MSG_GETDEFAULTDG_CONTROL / DAT_SETUPFILEXFER / MSG_RESETDG_CONTROL / DAT_SETUPFILEXFER / MSG_SET

Description

Describes the file format and file specification information for a transfer through a disk file.

Field Descriptions

FileName A complete file specifier to the target file. On Windows, be sure to include the complete pathname.

Format The format of the file the Source is to fill. Fill with the correct constant—as negotiated with the Source—of type TWFF_xxxx.

VRefNum The volume reference number for the file. This applies to Macintosh only. On Windows, fill the field with TWON_DONTCARE16.


Chapter 8

TW_SETUPMEMXFERtypedef struct { TW_UINT32 MinBufSize; TW_UINT32 MaxBufSize; TW_UINT32 Preferred;} TW_SETUPMEMXFER, FAR * pTW_SETUPMEMXFER;

Used by


Description

Provides the application information about the Source’s requirements and preferences regarding allocation of transfer buffer(s). The best applications will allocate buffers of the Preferred size. An application should never allocate a buffer smaller than MinBufSize. Some Sources may not be able to fill a buffer larger than MaxBufSize so a larger allocation is a waste of RAM (digital cameras or frame grabbers fit this category).

Sources should fill out all three fields as accurately as possible. If a Source can fill an indeterminately large buffer (hand scanners might do this), put a -1 in MaxBufSize.

Field Descriptions

MinBufSize The size of the smallest transfer buffer, in bytes, that a Source can be successful with. This will typically be the number of bytes in an uncompressed row in the block to be transferred. An application should never allocate a buffer smaller than this.

MaxBufSize The size of the largest transfer buffer, in bytes, that a Source can fill. If a Source can fill an arbitrarily large buffer, it might set this field to negative 1 to indicate this (a hand-held scanner might do this, depending on how long its cord is). Other Sources, such as frame grabbers, cannot fill a buffer larger than a certain size. Allocation of a transfer buffer larger than this value is wasteful.

Preferred The size of the optimum transfer buffer, in bytes. A smart application will allocate transfer buffers of this size, if possible. Buffers of this size will optimize the Source’s performance. Sources should be careful to put reasonable values in this field. Buffers that are 10’s of kbytes will be easier for applications to allocate than buffers that are 100’s or 1000’s of kbytes.


TW_STATUStypedef struct {

TW_UINT16 ConditionCode; // outputunion {

TW_UINT16 Data; // output (TWAIN 2.1 and newer)TW_UINT16 Reserved; // output (TWAIN 2.0 and older)

};} TW_STATUS, FAR * pTW_STATUS;

Used by

DG_CONTROL / DAT_STATUS / MSG_GETDG_CONTROL / DAT_STATUSUTF8 / MSG_GET (as part of TW_STATUSUTF8)

Description

Describes the status of a source.

Field Descriptions

ConditionCode TWCC_xxxx Condition Code describing the status.Data Valid for TWAIN 2.1 and later. This field contains additional

scanner-specific data. If there is no data, then this value must be zero. Reserved Only option for TWAIN 2.0 and earlier. If used it must be zero.


Chapter 8

TW_STATUSUTF8 typedef struct {

TW_STATUS Status;// input TW_UINT32 Size;// output TW_HANDLE UTF8string;// output

} TW_STATUSUTF8, FAR * pTW_STATUSUTF8;

Used by

DG_CONTROL / DAT_STATUSUTF8 / MSG_GET

Description

Translates the contents of Status into a localized UTF8string, with the total number of bytes in the string.

Field Descriptions

Status TW_STATUS data received from a previous call to DG_CONTROL / DAT_STATUS / MSG_GET.

Size Total number of bytes in the UTF8string, plus the terminating NUL byte. This is not the same as the total number of characters in the string.

UTF8string TW_HANDLE to a UTF-8 encoded localized string (based on TW_IDENTITY.Language or CAP_LANGUAGE). The Source allocates it, the Application frees it.


TW_TRANSFORMSTAGEtypedef struct { TW_DECODEFUNCTION Decode[3]; TW_FIX32 Mix[3][3];} TW_TRANSFORMSTAGE, FAR * pTW_TRANSFORMSTAGE;

Used by

Embedded in the TW_CIECOLOR structure

Description

Specifies the parametrics used for either the ABC or LMN transform stages. This structure parallels the TTransformStage structure definition in Appendix A.

Field Descriptions

Decode[3] Channel-specific transform parameters.

Mix[3][3] 3x3 matrix that specifies how channels are mixed in


Chapter 8

TW_USERINTERFACEtypedef struct { TW_BOOL ShowUI; TW_BOOL ModalUI; TW_HANDLE hParent;} TW_USERINTERFACE, FAR * pTW_USERINTERFACE;

Used by

DG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDSDG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS

Description

This structure is used to handle the user interface coordination between an application and a Source.

Field Descriptions

ShowUI Set to TRUE by the application if the Source should activate its built-in user interface. Otherwise, set to FALSE. Note that not all sources support ShowUI = FALSE. See the description of DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS for more information.

ModalUI If ShowUI is TRUE, then an application setting this to TRUE requests the Source to run Modal (no user access to the application’s windows while the Source is running).

hParent Microsoft Windows only: Application’s window handle. The Source designates the hWnd as its parent when creating the Source dialog.NOTE: Window handle allows Source’s user interface to be a proper child of the parent application.


TW_VERSIONtypedef struct { TW_UINT16 MajorNum; TW_UINT16 MinorNum; TW_UINT16 Language; TW_UINT16 Country; TW_STR32 Info;} TW_VERSION, FAR * pTW_VERSION;

Used by

This is embedded in the TW_IDENTITY data structure

Description

A general way to describe the version of software that is running.

Field Descriptions

Data Argument Types that Don’t Have Associated TW_Structures

Most of the DAT_xxxx components of the TWAIN operation triplets have a corresponding data structure whose name begins with TW_ and then uses the same suffix as the DAT_name. However, the following do not use that pattern.

DAT_IMAGEFILEXFERActs on NULL data.

DAT_IMAGENATIVEXFERUses a TW_UINT32 variable.

MajorNum This refers to your application or Source’s major revision number. e.g. The “2” in “version 2.1”.

MinorNum The incremental revision number of your application or Source. e.g. The “1” in “version 2.1”.

Language The primary language for your Source or application. e.g. TWLG_GER.

Country The primary country where your Source or application is intended to be distributed. e.g. Germany.

Info General information string - fill in as needed. e.g. “1.0b3 Beta release”.


Chapter 8

On Windows: In Win 3.1, the low word of this 32-bit integer is a handle variable to a DIB (Device Independent Bitmap) located in memory. For Win 95 the handles fill the entire field.

On Macintosh: This 32-bit integer is a handle to a Picture (a PicHandle). It is a QuickDraw picture located in memory.

DAT_NULLUsed by the Source to signal the need for an event to announce MSG_XFERREADY or MSG_CLOSEDSREQ. (Used on Windows only)

DAT_PARENTUsed by the DG_CONTROL / DAT_PARENT / MSG_OPENDSM and MSG_CLOSEDSM operations.

On Windows: They act on a variable of type TW_INT32. Prior to the operation, the application must write, a window handle to the application’s window that acts as the “parent” for the Source’s user interface. In Win 3.1 this would be in the low word, in Win 95 it will fill the entire field. (This must be done whether or not the Source’s user interface will be used. The Source Manager uses this window handle to signal the application when data is ready for transfer (MSG_XFERREADY) or the Source needs to be closed (MSG_CLOSEDSREQ)).

On Macintosh: These act on NULL data.

DAT_XFERGROUPUsed by the DG_CONTROL / DAT_XFERGROUP / MSG_GET operation. The data acted on by this operation is a variable of type TW_UINT32. (The same as a DG_xxxx designator.) The value of this variable is indeterminate prior to the operation. Following the operation, a single bit is set indicating the Data Group of the transfer.


Constants

Generic Constants

Constants

Flags used in TW_MEMORY

Palette types for TW_PALETTE8

Events for TW_DEVICEEVENT

See “CAP_DEVICEEVENT” on page 8-81.

Defined as Value

TWON_PROTOCOLMAJOR

TWON_PROTOCOLMINOR

2

1

TWON_ARRAYTWON_ENUMERATIONTWON_ONEVALUETWON_RANGE

3456

TWON_ICONIDTWON_DSMIDTWON_DSMCODEID

96246163

TWON_DONTCARE8TWON_DONTCARE16TWON_DONTCARE32

0xff0xffff0xffffffff

Defined as Value

TWMF_APPOWNSTWMF_DSMOWNSTWMF_DSOWNSTWMF_POINTERTWMF_HANDLE

0x00010x00020x00040x00080x0010

Defined as Value

TWPA_RGBTWPA_GRAYTWPA_CMY

012


Chapter 8

File Types for TW_FILESYSTEM

Query Support Bits

Note: These are bits in a mask.

Defined as Value

TWFY_CAMERATWFY_CAMERATOPTWFY_CAMERABOTTOMTWFY_CAMERAPREVIEWTWFY_DOMAINTWFY_HOSTTWFY_DIRECTORYTWFY_IMAGETWFY_UNKNOWN

012345678

Defined as ValueTWQC_GETTWQC_SETTWQC_GETDEFAULTTWQC_GETCURRENTTWQC_RESET

0x00010x00020x00040x00080x0010


ConType for Capability Container structures

ItemType for Capability Container structures

Direction for TW_PASSTHRU

Patch Codes for TW_PENDINGXFERS

Defined as ValueTWON_ARRAYTWON_ENUMERATIONTWON_ONEVALUETWON_RANGE

3456

Defined as Value

TWTY_INT8TWTY_INT16TWTY_INT32

0x00000x00010x0002

TWTY_UINT8TWTY_UINT16TWTY_UINT32

0x00030x00040x0005

TWTY_BOOL 0x0006

TWTY_FIX32

TWTY_FRAME

TWTY_STR32TWTY_STR64TWTY_STR128TWTY_STR255

TWTY_HANDLE

0x0007

0x0008

0x00090x000A0x000B0x000C

0x000F //Item is a TW_HANDLE

Defined as Value

TWDR_GETTWDR_SET

12

Defined as Value

TWEJ_NONETWEJ_MIDSEPERATORTWEJ_PATCH1TWEJ_PATCH2TWEJ_PATCH3TWEJ_PATCH4TWEJ_PATCH6TWEJ_PATCHT

0x00000x00010x00020x00030x00040x00050x00060x0007


Chapter 8

Triplet Constants

Data Groups (DG_)

Note: These are bits in a mask.

Data Group (DG_) Numeric ID

DG_CONTROLDG_IMAGEDG_AUDIO

0x0001L0x0002L0x0004L


Data Argument Types (DAT_)

Message (MSG_)

Version Data Group (DG_) Numeric ID

DAT_NULLDAT_CUSTOMBASE

0x00000x8000

DAT_CAPABILITYDAT_EVENTDAT_IDENTITYDAT_PARENTDAT_PENDINGXFERSDAT_SETUPMEMXFERDAT_SETUPFILEXFERDAT_STATUSDAT_USERINTERFACEDAT_XFERGROUPDAT_CUSTOMDSDATADAT_DEVICEEVENTDAT_FILESYSTEMDAT_PASSTHRU

0x00010x00020x00030x00040x00050x00060x00070x00080x00090x000A0x000C0x000D0x000E0x000F

2.0 DAT_CALLBACK 0x0010

2.1 DAT_STATUSUTF8 0x0011

DAT_IMAGEINFODAT_IMAGELAYOUTDAT_IMAGEMEMXFERDAT_IMAGENATIVEXFERDAT_IMAGEFILEXFERDAT_CIECOLORDAT_GRAYRESPONSEDAT_RGBRESPONSEDAT_JPEGCOMPRESSIONDAT_PALETTE8DAT_EXTIMAGEINFO

0x01010x01020x01030x01040x01050x01060x01070x01080x01090x010A0x010B

DAT_AUDIOFILEXFERDAT_AUDIOINFODAT_AUDIONATIVEXFER

0x02010x02020x0203

1.91

1.91

DAT_ICCPROFILE

DAT_IMAGEMEMFILEXFER

0x0401

0x0402


MSG_NULLMSG_CUSTOMBASE

0x00000x8000


Chapter 8

MSG_GETMSG_GETCURRENTMSG_GETDEFAULTMSG_GETFIRSTMSG_GETNEXTMSG_SETMSG_RESETMSG_QUERYSUPPORT

0x00010x00020x00030x00040x00050x00060x00070x0008

2.1 MSG_GETHELP 0x0009

2.1 MSG_GETLABEL 0x000A

2.1 MSG_GETGETLABELENUM 0x000B

MSG_XFERREADYMSG_CLOSEDSREQMSG_CLOSEDSOKMSG_DEVICEEVENT

0x01010x01020x01030x0104

MSG_OPENDSMMSG_CLOSEDSM

0x03010x0301

MSG_OPENDSMSG_CLOSEDSMSG_USERSELECT

0x04010x04020x0403

MSG_DISABLEDSMSG_ENABLEDSMSG_ENABLEDSUIONLY

0x05010x05020x0503

MSG_PROCESSEVENT 0x0601

MSG_ENDXFERMSG_STOPFEEDER

0x07010x0701

MSG_CHANGEDIRECTORYMSG_CREATEDIRECTORYMSG_DELETEMSG_FORMATMEDIAMSG_GETCLOSEMSG_GETFIRSTFILEMSG_GETINFOMSG_GETNEXTFILEMSG_RENAMEMSG_COPYMSG_AUTOMATICCAPTUREDIRECTORY

0x08010x08020x08030x08040x08050x08060x08070x08080x08090x080A0x080B

MSG_PASSTHRU 0x0901

1.91 MSG_RESETALL 0x0A01



Return Code and Condition Code Constants

Return Codes (TWRC_)

Condition Codes (TWCC_)

Return code Numeric ID

TWRC_CUSTOMBASE

TWRC_SUCCESSTWRC_FAILURETWRC_CHECKSTATUSTWRC_CANCELTWRC_DSEVENTTWRC_NOTDSEVENTTWRC_XFERDONETWRC_ENDOFLISTTWRC_INFONOTSUPPORTEDTWRC_DATANOTAVAILABLE

0x8000

0123456789

Version Return Code Numeric ID

TWCC_CUSTOMBASE 0x8000

TWCC_SUCCESSTWCC_BUMMERTWCC_LOWMEMORYTWCC_NODSTWCC_MAXCONNECTIONSTWCC_OPERATIONERRORTWCC_BADCAPTWCC_BADPROTOCOLTWCC_BADVALUETWCC_SEQERRORTWCC_BADDESTTWCC_CAPUNSUPPORTEDTWCC_CAPBADOPERATIONTWCC_CAPSEQERROR

01234569101112131415

1.81.81.81.81.81.81.81.8

TWCC_DENIEDTWCC_FILEEXISTSTWCC_FILENOTFOUNDTWCC_NOTEMPTYTWCC_PAPERJAMTWCC_PAPERDOUBLEFEEDTWCC_FILEWRITEERRORTWCC_CHECKDEVICEONLINE

1617181920212223

2.02.02.02.02.02.1

TWCC_INTERLOCKTWCC_DAMAGEDCORNERTWCC_FOCUSERRORTWCC_DOCTOOLIGHTTWCC_DOCTOODARKTWCC_NOMEDIA

242526272829


Chapter 8

Extended Image Information Constants

TWEI_Codes


TWEI_BARCODEXTWEI_BARCODEYTWEI_BARCODETEXTTWEI_BARCODETYPE

0x12000x12010x12020x1203

TWEI_DESHADETOPTWEI_DESHADELEFTTWEI_DESHADEHEIGHTTWEI_DESHADEWIDTHTWEI_DESHADESIZE

0x12040x12050x12060x12070x1208

TWEI_SPECKLESREMOVEDTWEI_HORZLINEXCOORDTWEI_HORZLINEYCOORDTWEI_HORZLINELENGTHTWEI_HORZLINETHICKNESSTWEI_VERTLINEXCOORDTWEI_VERTLINEYCOORDTWEI_VERTLINELENGTHTWEI_VERTLINETHICKNESS

0x12090x120A0x120B0x120C0x120D0x120E0x120F0x12100x1211

TWEI_PATCHCODETWEI_ENDORSEDTEXTTWEI_FORMCONFIDENCETWEI_FORMTEMPLATEMATCHTWEI_FORMTEMPLATEPAGEMATCHTWEI_FORMHORZDOCOFFSETTWEI_FORMVERTDOCOFFSETTWEI_BARCODECOUNTTWEI_BARCODECONFIDENCETWEI_BARCODEROTATIONTWEI_BARCODETEXTLENGTH

0x12120x12130x12140x12150x12160x12170x12180x12190x121A0x121B0x121C

TWEI_DESHADECOUNTTWEI_DESHADEBLACKCOUNTOLDTWEI_DESHADEBLACKCOUNTNEWTWEI_DESHADEBLACKRLMINTWEI_DESHADEBLACKRLMAXTWEI_DESHADEWHITECOUNTOLDTWEI_DESHADEWHITECOUNTNEWTWEI_DESHADEWHITERLMINTWEI_DESHADEWHITERLAVETWEI_DESHADEWHITERLMAX

0x121D0x121E0x121F0x12200x12210x12220x12230x12240x12250x1226


TWEI_BLACKSPECKLESREMOVEDTWEI_WHITESPECKLESREMOVEDTWEI_HORZLINECOUNTTWEI_VERTLINECOUNTTWEI_DESKEWSTATUSTWEI_SKEWORIGINALANGLETWEI_SKEWFINALANGLETWEI_SKEWCONFIDENCETWEI_SKEWWINDOWX1TWEI_SKEWWINDOWY1TWEI_SKEWWINDOWX2TWEI_SKEWWINDOWY2TWEI_SKEWWINDOWX3TWEI_SKEWWINDOWY3TWEI_SKEWWINDOWX4TWEI_SKEWWINDOWY4

0x12270x12280x12290x122A0x122B0x122C0x122D0x122E0x122F0x12300x12310x12320x12330x12340x12350x1236

TWEI_BOOKNAMETWEI_CHAPTERNUMBERTWEI_DOCUMENTNUMBERTWEI_PAGENUMBERTWEI_CAMERATWEI_FRAMENUMBERTWEI_FRAMETWEI_PIXELFLAVOR

0x12380x12390x123A0x123B0x123C0x123D0x123E0x123F

1.911.911.91

TWEI_ICCPROFILETWEI_LASTSEGMENT TWEI_SEGMENTNUMBER

0x12400x12410x1242

2.02.02.02.0

TWEI_MAGDATATWEI_MAGTYPETWEI_PAGESIDETWEI_FILESYSTEMSOURCE

0x12430x12440x12450x1246

2.12.1

TWEI_IMAGEMERGEDTWEI_MAGDATALENGTH

0x12470x1248



Chapter 8

TWEI_BARCODEROTATION

TWEI_DESKEWSTATUS

TWEI_MAGTYPE

TWEI_PATCHCODE

Capability Constants

Return Code Numeric ID

TWBCOR_ROT0TWBCOR_ROT90TWBCOR_ROT180TWBCOR_ROT270TWBCOR_ROTX

01234


TWDSK_SUCCESSTWDSK_REPORTONLYTWDSK_FAILTWDSK_DISABLED

0123


2.0 TWMD_MICR 0

2.1 TWMD_RAW 1

2.1 TWMD_INVALID 2


TWPCH_PATCH1TWPCH_PATCH2TWPCH_PATCH3TWPCH_PATCH4TWPCH_PATCH6TWPCH_PATCHT

012345

Version Constant Numeric ID

CAP_CUSTOMBASE 0x8000

CAP_XFERCOUNT 0x0001

ICAP_COMPRESSION 0x0101

ICAP_PIXELTYPE 0x0102

ICAP_UNITS 0x0103


ICAP_XFERMECH 0x0104

CAP_AUTHOR 0x1000

CAP_CAPTION 0x1001

CAP_FEEDERENABLED 0x1002

CAP_FEEDERLOADED 0x1003

CAP_TIMEDATE 0x1004

CAP_SUPPORTEDCAPS 0x1005

CAP_EXTENDEDCAPS 0x1006

CAP_AUTOFEED 0x1007

CAP_CLEARPAGE 0x1008

CAP_FEEDPAGE 0x1009

CAP_REWINDPAGE 0x100A

CAP_INDICATORS 0x100B

CAP_PAPERDETECTABLE 0x100D

CAP_UICONTROLABLE 0x100E

CAP_DEVICEONLINE 0x100F

CAP_AUTOSCAN 0x1010

CAP_THUMBNAILSENABLED 0x1011

CAP_DUPLEX 0x1012

CAP_DUPLEXENALBED 0x1013

CAP_ENABLEDSUIONLY 0x1014

CAP_CUSTOMEDSDATA 0x1015

CAP_ENDORSER 0x1016

CAP_JOBCONTROL 0x1017

CAP_ALARMS 0x1018

CAP_ALARMVOLUME 0x1019

CAP_AUTOMATICCAPTURE 0x101A

CAP_TIMEBEFOREFIRSTCAPTURE 0x101B

CAP_TIMEBETWEENCAPTURES 0x101C

CAP_CLEARBUFFERS 0x101D

CAP_MAXBATCHBUFFERS 0x101E



Chapter 8

CAP_DEVICEDATETIME 0x101F

CAP_POWERSUPPLY 0x1020

CAP_CAMERAPREVIEWUI 0x1021

CAP_DEVICEEVENT 0x1022

CAP_SERIALNUMBER 0x1024

CAP_PRINTER 0x1024

CAP_PRINTERENABLED 0x1026

CAP_PRINTERINDEX 0x1027

CAP_PRINTERMODE 0x1028

CAP_PRINTERSTRING 0x1029

CAP_PRINTERSUFFIX 0x102A

CAP_LANGUAGE 0x102B

CAP_FEEDERALIGNMENT 0x102C

CAP_FEEDERORDER 0x102D

CAP_REACQUIREALLOWED 0x1030

CAP_BATTERYMINUTES 0x1032

CAP_BATTERYPERCENTAGE 0x1033

1.91 CAP_CAMERASIDE 0x1034

1.91 CAP_SEGMENTED 0x1035

2.0 CAP_CAMERAENABLED 0x1036

2.0 CAP_CAMERAORDER 0x1037

2.0 CAP_MICRENABLED 0x1038

2.0 CAP_FEEDERPREP 0x1039

2.0 CAP_FEEDERPOCKET 0x103A

2.1 CAP_AUTOMATICSENSEMEDIUM 0x103B

2.1 CAP_CUSTOMINTERFACEGUID 0x103C

ICAP_AUTOBRIGHT 0x1100

ICAP_BRIGHTNESS 0x1101

ICAP_CONTRAST 0x1103

ICAP_CUSTHALFTONE 0x1104

ICAP_EXPOSURETIME 0x1105



ICAP_FILTER 0x1106

ICAP_FLASHUSED 0x1107

ICAP_GAMMA 0x1108

ICAP_HALFTONES 0x1109

ICAP_HIGHLIGHT 0x110A

ICAP_IMAGEFILEFORMAT 0x110C

ICAP_LAMPSTATE 0x110D

ICAP_LIGHTSOURCE 0x110E

ICAP_ORIENTATION 0x1110

ICAP_PHYSICALWIDTH 0x1111

ICAP_PHYSICALHEIGHT 0x1112

ICAP_SHADOW 0x1113

ICAP_FRAMES 0x1114

ICAP_XNATIVERESOLUTION 0x1116

ICAP_YNATIVERESOLUTION 0x1117

ICAP_XRESOLUTION 0x1118

ICAP_YRESOLUTION 0x1119

ICAP_MAXFRAMES 0x111A

ICAP_TILES 0x111B

ICAP_BITORDER 0x111C

ICAP_CCITTKFACTOR 0x111D

ICAP_LIGHTPATH 0x111E

ICAP_PIXELFLAVOR 0x111F

ICAP_PLANARCHUNKY 0x1120

ICAP_ROTATION 0x1121

ICAP_SUPPORTEDSIZES 0x1122

ICAP_THRESHOLD 0x1123

ICAP_XSCALING 0x1124

ICAP_YSCALING 0x1125

ICAP_BITORDERCODES 0x1126

ICAP_PIXELFLAVORCODES 0x1127



Chapter 8

ICAP_JPEGPIXELTYPE 0x1128

ICAP_TIMEFILL 0x112A

ICAP_BITDEPTH 0x112B

ICAP_UNDEFINEDIMAGESIZE 0x112C

ICAP_IMAGEDATASET 0x112D

ICAP_EXTIMAGEINFO 0x112E

ICAP_MINUMUMHEIGHT 0x112F

ICAP_MINIMUMWIDTH 0x1130

ICAP_FLIPROTATION 0x1131

ICAP_AUTODISCARDBLANKPAGES 0x1134

ICAP_BARCODEDETECTIONENABLED 0x1136

ICAP_SUPPORTEDBARCODETYPES 0x1137

ICAP_BARCODEMAXSEARCHPRIORITIES 0x1138

ICAP_BARCODESEARCHPRIORITIES 0x1139

ICAP_BARCODESEARCHMODE 0x113A

ICAP_BARCODEMAXRETRIES 0x113B

ICAP_BARCODETIMEOUT 0x113C

ICAP_ZOOMFACTOR 0x113D

ICAP_BITDEPTHREDUCTION 0x113E

ICAP_PATCHCODEDETECTIONENABLED 0x113F

ICAP_SUPPORTEDPATCHCODETYPES 0x1140

ICAP_PATCHCODEMAXSEARCHPRIORITIE 0x1141

ICAP_PATCHCODESEARCHPRIORITIES 0x1142

ICAP_PATCHCODESEARCHMODE 0x1143

ICAP_PATCHCODEMAXRETRIES 0x1144

ICAP_PATCHCODETIMEOUT 0x1145

ICAP_FLASHUSED2 0x1146

ICAP_IMAGEFILTER 0x1147

ICAP_NOISEFILTER 0x1148

ICAP_OVERSCAN 0x1149

ICAP_AUTOMATICBORDERDETECTION 0x1150



ICAP_AUTOMATICDESKEW 0x1151

ICAP_AUTOMATICROTATE 0x1152

ICAP_JPEGQUALITY 0x1153

1.91 ICAP_FEEDERTYPE 0x1154

1.91 ICAP_ICCPROFILE 0x1155

2.0 ICAP_AUTOSIZE 0x1156

2.1 ICAP_AUTOMATICCROPUSESFRAME 0x1157

2.1 ICAP_AUTOMATICLENGTHDETECTION 0x1158

2.1 ICAP_AUTOMATICCOLORENABLED 0x1159

2.1 AUTOMATICCOLORNONCOLORPIXELTYPE 0x115A

2.1 ICAP_COLORMANAGEMENTENABLED 0x115B

2.1 ICAP_IMAGEMERGE 0x115C

2.1 ICAP_IMAGEMERGEHEIGHTTHRESHOLD 0x115D

2.1 ICAP_SUPPORTEDEXTIMAGEINFO 0x115E

0 ACAP_XFERMECH 0x1202



Chapter 8

CAP_ALARMS

CAP_CAMERASIDE

CAP_CLEARBUFFERS

Constant Numeric ID

TWAL_ALARMTWAL_FEEDERERRORTWAL_FEEDERWARNINGTWAL_BARCODETWAL_DOUBLEFEEDTWAL_JAMTWAL_PATCHCODETWAL_POWERTWAL_SKEW

012345678


1.911.911.91

TWCS_BOTHTWCS_TOPTWCS_BOTTOM

012

Constant Numeric ID

TWCB_AUTOTWCB_CLEARTWCB_NOCLEAR

012


CAP_DEVICEEVENT

CAP_DUPLEX

CAP_FEEDERALIGNMENT

CAP_FEEDERORDER

Constant Numeric ID

TWDE_CUSTOMEVENTS 0x8000

TWDE_CHECKAUTOMATICCAPTURE TWDE_CHECKBATTERYTWDE_CHECKDEVICEONLINE TWDE_CHECKFLASH TWDE_CHECKPOWERSUPPLYTWDE_CHECKRESOLUTION

012345

TWDE_DEVICEADDEDTWDE_DEVICEOFFLINETWDE_DEVICEREADY TWDE_DEVICEREMOVED

6789

TWDE_IMAGECAPTUREDTWDE_IMAGEDELETED TWDE_PAPERDOUBLEFEED TWDE_PAPERJAM TWDE_LAMPFAILURETWDE_POWERSAVETWDE_POWERSAVENOTIFY

10111213141516

Constant Numeric ID

TWDX_NONETWDX_1PASSDUPLEXTWDX_2PASSDUPLEX

012

Constant Numeric ID

TWFA_NONETWFA_LEFTTWFA_CENTERTWFA_RIGHT

0123

Constant Numeric ID

TWFO_FIRSTPAGEFIRSTTWFO_LASTPAGEFIRST

01


Chapter 8

CAP_FEEDERPOCKET

CAP_JOBCONTROL

CAP_LANGUAGE

See “Language Constants” on page 8-91.

Constant Numeric ID

TWFP_POCKETERRORTWFP_POCKET1TWFP_POCKET2TWFP_POCKET3TWFP_POCKET4TWFP_POCKET5TWFP_POCKET6TWFP_POCKET7TWFP_POCKET8TWFP_POCKET9TWFP_POCKET10TWFP_POCKET11TWFP_POCKET12TWFP_POCKET13TWFP_POCKET14TWFP_POCKET15TWFP_POCKET16

012345678910111213141516

Constant Numeric ID

TWJC_NONETWJC_JSICTWJC_JSISTWJC_JSXCTWJC_JSXS

01234


CAP_POWERSUPPLY

CAP_PRINTER

CAP_PRINTERMODE

CAP_SEGMENTED

ICAP_AUTODISCARDBLANKPAGES

ICAP_AUTOSIZE

Constant Numeric ID

TWPS_EXTERNALTWPS_BATTERY

01

Constant Numeric ID

TWPR_IMPRINTERTOPBEFORETWPR_IMPRINTERTOPAFTERTWPR_IMPRINTERBOTTOMBEFORETWPR_IMPRINTERBOTTOMAFTERTWPR_ENDORSERTOPBEFORETWPR_ENDORSERTOPAFTERTWPR_ENDORSERBOTTOMBEFORETWPR_ENDORSERBOTTOMAFTER

01234567

Constant Numeric ID

TWPM_SINGLESTRINGTWPM_MULTISTRINGTWPM_COMPOUNDSTRING

012


1.911.91

TWSG_NONETWSG_AUTO

01

Constant Numeric ID

TWBP_DISABLETWBP_AUTO

-2-1


2.02.02.0

TWAS_NONETWAS_AUTOTWAS_CURRENT

012


Chapter 8

ICAP_BARCODESEARCHMODE

ICAP_SUPPORTEDBARCODETYPES

ICAP_BITDEPTHREDUCTION

ICAP_BITORDER

Constant Numeric ID

TWBD_HORZTWBD_VERTTWBD_HORZVERTTWBD_VERTHORZ

0123

Constant Numeric ID

TWBT_3OF9TWBT_2OF5INTERLEAVEDTWBT_2OF5NONINTERLEAVEDTWBT_CODE93TWBT_CODE128TWBT_UCC128TWBT_CODABARTWBT_UPCATWBT_UPCETWBT_EAN8TWBT_EAN13TWBT_POSTNETTWBT_PDF417TWBT_2OF5INDUSTRIALTWBT_2OF5MATRIXTWBT_2OF5DATALOGICTWBT_2OF5IATATWBT_3OF9FULLASCIITWBT_CODABARWITHSTARTSTOPTWBT_MAXICODE

012345678910111213141516171819

Constant Numeric ID

TWBR_THRESHOLDTWBR_HALFTONETWBR_CUSTHALFTONETWBR_DIFFUSION

0123

Constant Numeric ID

TWBO_LSBFIRSTTWBO_MSBFIRST

01


ICAP_COMPRESSION

ICAP_FEEDERTYPE

ICAP_FILTER

ICAP_FLASHUSED2

Constant Numeric ID

TWCP_NONETWCP_PACKBITSTWCP_GROUP31DTWCP_GROUP31DEOLTWCP_GROUP32DTWCP_GROUP4TWCP_JPEGTWCP_LZWTWCP_JBIGTWCP_PNGTWCP_RLE4TWCP_RLE8TWCP_BITFIELDS

0123456789101112


1.911.91

TWFE_GENERALTWFE_PHOTO

01

Constant Numeric ID

TWFT_REDTWFT_GREENTWFT_BLUETWFT_NONETWFT_WHITETWFT_CYANTWFT_MAGENTATWFT_YELLOWTWFT_BLACK

012345678

Constant Numeric ID

TWFL_NONETWFL_OFFTWFL_ONTWFL_AUTOTWFL_REDEYE

01234


Chapter 8

ICAP_FLIPROTATION

ICAP_ICCPROFILE

ICAP_IMAGEFILEFORMAT

ICAP_IMAGEFILTER

Constant Numeric ID

TWFR_BOOKTWFR_FANFOLD

01

Constant Numeric ID

1.911.911.91

TWIC_NONETWIC_LINKTWIC_EMBED

012


1.911.91

1.911.912.02.1

TWFF_TIFFTWFF_PICTTWFF_BMPTWFF_XBMTWFF_JFIFTWFF_FPXTWFF_TIFFMULTITWFF_PNGTWFF_SPIFFTWFF_EXIFTWFF_PDFTWFF_JP2removedTWFF_JPXTWFF_DEVAVUTWFF_PDFATWFF_PDFA2

012345678910111213141516

Constant Numeric ID

TWIF_NONETWIF_AUTOTWIF_LOWPASSTWIF_BANDPASSTWIF_HIGHPASSTWIF_TEXTTWIF_FINELINE

01234TWIF_BANDPASSTWIF_HIGHPASS


ICAP_IMAGEMERGE

ICAP_JPEGQUALITY

ICAP_LIGHTPATH

ICAP_LIGHTSOURCE

ICAP_NOISEFILTER


2.12.12.12.12.1

TWIM_NONETWIM_FRONTONTOP TWIM_FRONTONBOTTOM TWIM_FRONTONLEFT TWIM_FRONTONRIGHT

01234

Constant Numeric ID

TWJQ_UNKNOWNTWJQ_LOWTWJQ_MEDIUMTWJQ_HIGH

-4-3-2-1

Constant Numeric ID

TWLP_REFLECTIVETWLP_TRANSMISSIVE

01

Constant Numeric ID

TWLS_REDTWLS_GREENTWLS_BLUETWLS_NONETWLS_WHITETWLS_UVTWLS_IR

0123456

Constant Numeric ID

TWNF_NONETWNF_AUTOTWNF_LONEPIXELTWNF_MAJORITYRULE

0123


Chapter 8

ICAP_ORIENTATION

ICAP_OVERSCAN

ICAP_PLANARCHUNKY

ICAP_PIXELFLAVOR


2.02.02.0

TWOR_ROT0TWOR_ROT90TWOR_ROT180TWOR_ROT270TWOR_PORTRAITTWOR_LANDSCAPETWOR_AUTOTWOR_AUTOTEXTTWOR_AUTOPICTURE

0123TWOR_ROT0TWOR_ROT270456

Constant Numeric ID

TWOV_NONETWOV_AUTOTWOV_TOPBOTTOMTWOV_LEFTRIGHTTWOV_ALL

01234

Constant Numeric ID

TWPC_CHUNKYTWPC_PLANAR

01

Constant Numeric ID

TWPF_CHOCOLATETWPF_VANILLA

01


ICAP_PIXELTYPE

ICAP_SUPPORTEDSIZES


1.911.912.0

TWPT_BWTWPT_GRAYTWPT_RGBTWPT_PALETTETWPT_CMYTWPT_CMYKTWPT_YUVTWPT_YUVKTWPT_CIEXYZTWPT_LABTWPT_SRGBTWPT_YCBCRTWPT_INFRARED

0123456789101116


TWSS_NONETWSS_A4TWSS_JISB5TWSS_USLETTERTWSS_USLEGALTWSS_A5TWSS_ISOB4TWSS_ISOB6

01234567

// removedTWSS_USLEDGERTWSS_USEXECUTIVETWSS_A3TWSS_ISOB3TWSS_A6TWSS_C4TWSS_C5TWSS_C6

910111213141516

// 1.8 AdditionsTWSS_4A0TWSS_2A0TWSS_A0TWSS_A1TWSS_A2TWSS_A7TWSS_A8TWSS_A9TWSS_A10

171819202122232425


Chapter 8

TWSS_ISOB0TWSS_ISOB1TWSS_ISOB2TWSS_ISOB5TWSS_ISOB7TWSS_ISOB8TWSS_ISOB9TWSS_ISOB10

2627282930313233

TWSS_JISB0TWSS_JISB1TWSS_JISB2TWSS_JISB3TWSS_JISB4TWSS_JISB6TWSS_JISB7TWSS_JISB8TWSS_JISB9TWSS_JISB10

34353637383940414243

TWSS_C0TWSS_C1TWSS_C2TWSS_C3TWSS_C7TWSS_C8TWSS_C9TWSS_C10TWSS_USEXECUTIVETWSS_BUSINESSCARD

44454647484950515253

2.1 TWSS_MAXSIZE 54



ICAP_XFERMECH

ICAP_UNITS

Language Constants

Language


1.91

TWSX_NATIVETWSX_FILETWSX_MEMORY//removedTWSX_MEMFILE

012

4


1.91

TWUN_INCHESTWUN_CENTIMETERSTWUN_PICASTWUN_POINTSTWUN_TWIPSTWUN_PIXELSTWUN_MILLIMETERS

0123456

Language (defined as)

TWLG_USERLOCALETWLG_DANTWLG_DUTTWLG_ENGTWLG_FCFTWLG_FINTWLG_FRNTWLG_GERTWLG_ICETWLG_ITNTWLG_NORTWLG_PORTWLG_SPATWLG_SWETWLG_USA

-1012345678910111213


Chapter 8

TWLG_AFRIKAANSTWLG_ALBANIATWLG_ARABICTWLG_ARABIC_ALGERIATWLG_ARABIC_BAHRAINTWLG_ARABIC_EGYPTTWLG_ARABIC_IRAQTWLG_ARABIC_JORDANTWLG_ARABIC_KUWAITTWLG_ARABIC_LEBANONTWLG_ARABIC_LIBYATWLG_ARABIC_MOROCCO

141516171819202122232425

TWLG_ARABIC_OMANTWLG_ARABIC_QATARTWLG_ARABIC_SAUDIARABIATWLG_ARABIC_SYRIATWLG_ARABIC_TUNISIATWLG_ARABIC_UAETWLG_ARABIC_YEMENTWLG_BASQUETWLG_BYELORUSSIANTWLG_BULGARIANTWLG_CATALANTWLG_CHINESE

262728293031323334353637

TWLG_CHINESE_HONGKONGTWLG_CHINESE_PRCTWLG_CHINESE_SINGAPORETWLG_CHINESE_SIMPLIFIEDTWLG_CHINESE_TAIWANTWLG_CHINESE_TRADITIONALTWLG_CROATIATWLG_CZECHTWLG_DANISHTWLG_DUTCHTWLG_DUTCH_BELGIANTWLG_ENGLISHTWLG_ENGLISH_AUSTRALIANTWLG_ENGLISH_CANADIANTWLG_ENGLISH_IRELANDTWLG_ENGLISH_NEWZEALAND

3839404142434445TWLG_DANTWLG_DUT46TWLG_ENG47484950



TWLG_ENGLISH_SOUTHAFRICATWLG_ENGLISH_UKTWLG_ENGLISH_USATWLG_ESTONIANTWLG_FAEROESETWLG_FARSITWLG_FINNISHTWLG_FRENCHTWLG_FRENCH_BELGIANTWLG_FRENCH_CANADIANTWLG_FRENCH_LUXEMBOURGTWLG_FRENCH_SWISSTWLG_GERMANTWLG_GERMAN_AUSTRIANTWLG_GERMAN_LUXEMBOURGTWLG_GERMAN_LIECHTENSTEINTWLG_GERMAN_SWISSTWLG_GREEKTWLG_HEBREWTWLG_HUNGARIANTWLG_ICELANDICTWLG_INDONESIANTWLG_ITALIANTWLG_ITALIAN_SWISS

5152TWLG_USA535455TWLG_FINTWLG_FRN56TWLG_FCF5758TWLG_GER59606162636465TWLG_ICE66TWLG_ITN67

TWLG_JAPANESETWLG_KOREANTWLG_KOREAN_JOHABTWLG_LATVIANTWLG_LITHUANIANTWLG_NORWEGIANTWLG_NORWEGIAN_BOKMALTWLG_NORWEGIAN_NYNORSKTWLG_POLISH

6869707172TWLG_NOR737475

TWLG_PORTUGUESETWLG_PORTUGUESE_BRAZILTWLG_ROMANIANTWLG_RUSSIANTWLG_SERBIAN_LATINTWLG_SLOVAKTWLG_SLOVENIANTWLG_SPANISHTWLG_SPANISH_MEXICANTWLG_SPANISH_MODERNTWLG_SWEDISHTWLG_THAITWLG_TURKISH

TWLG_POR767778798081TWLG_SPA8283TWLG_SWE8485



Chapter 8

TWLG_UKRANIANTWLG_ASSAMESETWLG_BENGALITWLG_BIHARITWLG_BODOTWLG_DOGRITWLG_GUJARATITWLG_HARYANVITWLG_HINDITWLG_KANNADATWLG_KASHMIRITWLG_MALAYALAMTWLG_MARATHITWLG_MARWARITWLG_MEGHALAYAN

8687888990919293949596979899100

TWLG_MIZOTWLG_NAGATWLG_ORISSITWLG_PUNJABITWLG_PUSHTUTWLG_SERBIAN_CYRILLICTWLG_SIKKIMITWLG_SWEDISH_FINLANDTWLG_TAMILTWLG_TELUGUTWLG_TRIPURITWLG_URDUTWLG_VIETNAMESE

101102103104105106107108109110111112113



Country

Country Numeric ID

TWCY_AFGHANISTAN

TWCY_ALGERIA

TWCY_AMERICANSAMOA

TWCY_ANDORRA

TWCY_ANGOLA

1001

213

684

33

1002

TWCY_ANGUILLA

TWCY_ANTIGUA

TWCY_ARGENTINA

TWCY_ARUBA

TWCY_ASCENSIONI

TWCY_AUSTRALIA

8090

8091

54

297

247

61

TWCY_AUSTRIA

TWCY_BAHAMAS

TWCY_BAHRAIN

TWCY_BANGLADESH

TWCY_BARBADOS

TWCY_BELGIUM

TWCY_BELIZE

TWCY_BENIN

TWCY_BERMUDA

TWCY_BHUTAN

TWCY_BOLIVIA

TWCY_BOTSWANA

TWCY_BRITAIN

TWCY_BRITVIRGINIS

TWCY_BRAZIL

43

8092

973

880

8093

32

501

229

8094

1003

591

267

6

8095

55

TWCY_BRUNEI

TWCY_BULGARIA

TWCY_BURKINAFASO

TWCY_BURMA

TWCY_BURUNDI

673

359

1004

1005

1006

TWCY_CAMAROON

TWCY_CANADA

TWCY_CAPEVERDEIS

TWCY_CAYMANIS

TWCY_CENTRALAFREP

237

2

238

8096

1007


Chapter 8

TWCY_CHAD

TWCY_CHILE

TWCY_CHINA

TWCY_CHRISTMASIS

TWCY_COCOSIS

TWCY_COLOMBIA

TWCY_COMOROS

TWCY_CONGO

1008

56

86

1009

1009

57

1010

1011

TWCY_COOKIS

TWCY_COSTARICA

TWCY_CUBA

TWCY_CYPRUS

TWCY_CZECHOSLOVAKIA

TWCY_DENMARK

TWCY_DJIBOUTI

TWCY_DOMINICA

TWCY_DOMINCANREP

TWCY_EASTERIS

TWCY_ECUADOR

TWCY_EGYPT

TWCY_ELSALVADOR

TWCY_EQGUINEA

TWCY_ETHIOPIA

TWCY_FALKLANDIS

TWCY_FAEROEIS

TWCY_FIJIISLANDS

TWCY_FINLAND

1012

506

5

357

42

45

1013

8097

8098

1014

593

20

503

1015

251

1016

298

679

358

TWCY_FRANCE

TWCY_FRANTILLES

TWCY_FRGUIANA

TWCY_FRPOLYNEISA

TWCY_FUTANAIS

33

596

594

689

1043

TWCY_GABON

TWCY_GAMBIA

TWCY_GERMANY

TWCY_GHANA

TWCY_GIBRALTER

TWCY_GREECE

241

220

49

233

350

30

Country Numeric ID


TWCY_GREENLAND

TWCY_GRENADA

TWCY_GRENEDINES

TWCY_GUADELOUPE

TWCY_GUAM

TWCY_GUANTANAMOBAY

TWCY_GUATEMALA

TWCY_GUINEA

TWCY_GUINEABISSAU

TWCY_GUYANA

TWCY_HAITI

TWCY_HONDURAS

299

8099

8015

590

671

5399

502

224

1017

592

509

504

TWCY_HONGKONG

TWCY_HUNGARY

TWCY_ICELAND

TWCY_INDIA

TWCY_INDONESIA

TWCY_IRAN

TWCY_IRAQ

TWCY_IRELAND

TWCY_ISRAEL

TWCY_ITALY

TWCY_IVORYCOAST

TWCY_JAMAICA

TWCY_JAPAN

TWCY_JORDAN

TWCY_KENYA

TWCY_KIRIBATI

TWCY_KOREA

852

36

354

91

62

98

964

353

972

39

225

8010

81

962

254

1018

82

TWCY_KUWAIT

TWCY_LAOS

TWCY_LEBANON

TWCY_LIBERIA

965

1019

1020

231

Country Numeric ID


Chapter 8

TWCY_LIBYA

TWCY_LIECHTENSTEIN

TWCY_LUXENBOURG

TWCY_MACAO

TWCY_MADAGASCAR

TWCY_MALAWI

TWCY_MALAYSIA

TWCY_MALDIVES

TWCY_MALI

TWCY_MALTA

TWCY_MARSHALLIS

TWCY_MAURITANIA

TWCY_MAURITIUS

TWCY_MEXICO

218

41

352

853

1021

265

60

960

1022

356

692

1023

230

3

TWCY_MICRONESIA

TWCY_MIQUELON

TWCY_MONACO

TWCY_MONGOLIA

TWCY_MONTSERRAT

TWCY_MOROCCO

TWCY_MOZAMBIQUE

TWCY_NAMIBIA

TWCY_NAURU

TWCY_NEPAL

691

508

33

1024

8011

212

1025

264

1026

977

TWCY_NETHERLANDS

TWCY_NETHANTILLES

TWCY_NEVIS

TWCY_NEWCALEDONIA

TWCY_NEWZEALAND

31

599

8012

687

64

TWCY_NICARAGUA

TWCY_NIGER

TWCY_NIGERIA

TWCY_NIUE

TWCY_NORFOLKI

TWCY_NORWAY

505

227

234

1027

1028

47

Country Numeric ID


TWCY_OMAN

TWCY_PAKISTAN

TWCY_PALAU

TWCY_PANAMA

968

92

1029

507

TWCY_PARAGUAY

TWCY_PERU

TWCY_PHILLIPPINES

TWCY_PITCAIRNIS

TWCY_PNEWGUINEA

TWCY_POLAND

TWCY_PORTUGAL

TWCY_QATAR

TWCY_REUNIONI

TWCY_ROMANIA

TWCY_RWANDA

595

51

63

1030

675

48

351

974

1031

40

250

TWCY_SAIPAN

TWCY_SANMARINO

TWCY_SAOTOME

TWCY_SAUDIARABIA

TWCY_SENEGAL

TWCY_SEYCHELLESIS

TWCY_SIERRALEONE

TWCY_SINGAPORE

TWCY_SOLOMONIS

TWCY_SOMALI

TWCY_SOUTHAFRICA

TWCY_SPAIN

670

39

1033

966

221

1034

1035

65

1036

1037

27

34

TWCY_SRILANKA

TWCY_STHELENA

TWCY_STKITTS

TWCY_STLUCIA

TWCY_STPIERRE

TWCY_STVINCENT

TWCY_SUDAN

TWCY_SURINAME

TWCY_SWAZILAND

TWCY_SWEDEN

94

1032

8013

8014

508

8015

1038

597

268

46

Country Numeric ID


Chapter 8

TWCY_SWITZERLAND

TWCY_SYRIA

TWCY_TAIWAN

TWCY_TANZANIA

TWCY_THAILAND

TWCY_TOBAGO

TWCY_TOGO

TWCY_TONGAIS

TWCY_TRINIDAD

TWCY_TUNISIA

TWCY_TURKEY

TWCY_TURKSCAICOS

TWCY_TUVALU

TWCY_UGANDA

TWCY_USSR

41

1039

886

255

66

8016

228

676

8016

216

90

8017

1040

256

7

TWCY_UAEMIRATES

TWCY_UNITEDKINGDOM

TWCY_USA

TWCY_URUGUAY

TWCY_VANUATU

TWCY_VATICANCITY

TWCY_VENEZUELA

TWCY_WAKE

TWCY_WALLISIS

TWCY_WESTERNSAHARA

TWCY_WESTERNSAMOA

TWCY_YEMEN

TWCY_YUGOSLAVIA

971

44

1

598

1041

39

58

1042

1043

1044

1045

1046

38

TWCY_ZAIRE

TWCY_ZAMBIA

TWCY_ZIMBABWE

TWCY_ALBANIA

TWCY_ARMENIA

TWCY_AZERBAIJAN

243

260

263

355

374

994

TWCY_BELARUS

TWCY_BOSNIAHERZGO

TWCY_CAMBODIA

TWCY_CROATIA

375

387

855

385

Country Numeric ID


Deprecated ItemsThese items are maintained because after something is added to TWAIN both its name and numeric id (if any) cannot be reused for any other purpose. However, even though they should not be used in applications and drivers, they must be included in a depreciated section in any compliant TWAIN include file. This helps ensure compatibility among all versions of TWAIN drivers and applications, and prevents collisions as new names and numbers are added to the Specification.

At this time the most notable depreciation is the DAT_SETUPFILEXFER2 and all related items. These were added in 1.9 to help with the Macintosh. It was subsequently decided that it wasn’t very useful (and no one was using it), so to cut down on confusion it’s been removed.

Platform Dependent Definitions and Typedefs#ifdef WIN32

#define TW_HUGE

TWCY_CZECHREPUBLIC

TWCY_DIEGOGARCIA

TWCY_ERITREA

420

246

291

TWCY_ESTONIA

TWCY_GEORGIA

TWCY_LATVIA

TWCY_LESOTHO

TWCY_LITHUANIA

TWCY_MACEDONIA

TWCY_MAYOTTEIS

TWCY_MOLDOVA

TWCY_MYANMAR

TWCY_NORTHKOREA

TWCY_PUERTORICO

TWCY_RUSSIA

TWCY_SERBIA

TWCY_SLOVAKIA

TWCY_SLOVENIA

TWCY_SOUTHKOREA

TWCY_UKRAINE

TWCY_USVIRGINIS

TWCY_VIETNAM

372

995

371

266

370

389

269

373

95

850

787

7

381

421

386

82

380

340

84

Country Numeric ID


Chapter 8

#else

#define TW_HUGE huge

#endif

typedef BYTE TW_HUGE * HPBYTE;

typedef void TW_HUGE * HPVOID;

String typestypedef unsigned char TW_STR1024[1026], FAR *pTW_STR1026;typedef wchar_t TW_UNI512[512], FAR *pTW_UNI512;

Constants

Note: For a description of these constants see the previous version of the TWAIN specification.

Capability Argument Constants

ACAP_AUDIOFILEFORMAT

Constant Nnumeric ID

TWAF_WAVTWAF_AIFFTWAF_AUTWAF_SND

0123

Section (defined as)

Data Argument Types (DAT_)

DAT_SETUPFILEXFER2DAT_TWUNKIDENTITY

0x301Ox000B

ItemTypes for Capability Container structures

TWTY_STR1024TWTY_UNI512

0x000d0x000e

Capabilities CAP_SUPPORTEDCAPSEXT

CAP_FILESYSTEM

0x100c

0x????Messages MSG_INVOKE_CALLBACK

MSG_CHECKSTATUS0x09030x0201


Structurestypedef struct {

TW_MEMREF FileName;

TW_UINT16 FileNameType;

TW_UINT16 Format;

TW_INT16 VRefNum;

TW_UINT32 parID;

} TW_SETUPFILEXFER2, FAR * pTW_SETUPFILEXFER2;

typedef struct {

TW_IDENTITY identity;

TW_STR255 dsPath;

} TW_TWUNKIDENTITY, FAR * pTW_TWUNKIDENTITY;

typedef struct {

TW_INT8 destFlag;

Capability values TWSX_FILE2

TWFS_FILESYSTEMTWFS_RECURSIVEDELETETWPT_BGRTWPT_CIELABTWPT_CIELUVTWPT_YCBCR

TWSS_BTWSS_B5LETTERTWSS_A4LETTERTWSS_B3TWSS_B4TWSS_B6

TWLG_DANTWLG_DUTTWLG_ENGTWLG_USATWLG_FINTWLG_FRNTWLG_FCFTWLG_GERTWLG_ICETWLG_ITNTWLG_NORTWLG_PORTWLG_SPATWLG_SWE

3

01

12131415

8TWSS_JISB5TWSS_A4TWSS_ISOB3TWSS_ISOB4TWSS_ISOB6

TWLG_DANISHTWLG_DUTCHTWLG_ENGLISHTWLG_ENGLISH_USATWLG_FINNISHTWLG_FRENCHTWLG_FRENCH_CANADIANTWLG_GERMANTWLG_ICELANDICTWLG_ITALIANTWLG_NORWEGIANTWLG_PORTUGUESETWLG_SPANISHTWLG_SWEDISH


Chapter 8

TW_IDENTITY dest;

TW_INT32 dataGroup;

TW_INT16 dataArgType;

TW_INT16 message;

TW_INT32 pDataSize;

} TW_TWUNKDSENTRYPARAMS, FAR * pTW_TWUNKDSENTRYPARAMS;

typedef struct {

TW_UINT16 returnCode;

TW_UINT16 conditionCode;

TW_INT32 pDataSize;

} TW_TWUNKDSENTRYRETURN, FAR * pTW_TWUNKDSENTRYRETURN;

typedef struct {

TW_UINT16 Cap;

TW_UINT16 Properties;

} TW_CAPEXT, FAR * pTW_CAPEXT;

typedef struct {

TW_STR255 FileName;

TW_UINT16 Format;

TW_INT16 VRefNum;

} TW_SETUPAUDIOFILEXFER, FAR * pTW_SETUPAUDIOFILEXFER;


9Extended Image Information Definitions

Chapter ContentsTWAIN 1.7 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-1TWAIN 1.9 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-12TWAIN 1.91 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-16TWAIN 2.0 Extended Image Attribute Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9-17

The following sections contain information about extended image attributes.

TWAIN 1.7 Extended Image Attribute CapabilitiesThe following extended image attribute capabilities have been defined. If a data source wishes to create additional custom image attribute capabilities, it should define its TWEI_CUSTOMxxx identifiers with a base starting ID of TWEI_CUSTOM+(x) where x is a unique positive number defined by the data source.

For all extended image attributes see: DG_IMAGE/DAT_EXTIMAGEINFO/MSG_GET


Chapter 9

Bar Code Recognition

TWEI_BARCODECOUNT

TWEI_BARCODECONFIDENCE

TWEI_BARCODEROTATION

TWEI_BARCODETEXTLENGTH

TWEI_BARCODETEXT

Description Returns the number of bar codes found on the document image. A value of 0 means the bar code engine was enabled but that no bar codes were found. A value of -1 means the bar code engine was not enabled.

Value Type: TW_UINT32

Allowed Values: >=0

Description This number reflects the degree of certainty the bar code engine has in the accuracy of the information obtained from the scanned image and ranges from 0 (no confidence) to 100 (supreme confidence). The Source may return a value of -1 if it does not support confidence reporting.


Allowed Values: >=0

Description The bar code’s orientation on the scanned image is described in reference to a Western-style interpretation of the image.


Allowed Values: TWBCOR_ROT0 Normal reading orientationTWBCOR_ROT90 Rotated 90 degrees clockwiseTWBCOR_ROT180 Rotated 180 degrees clockwiseTWBCOR_ROT270 Rotated 270 degrees clockwiseTWBCOR_ROTX The orientation is not known.

Description The number of ASCII characters derived from the bar code.


Allowed Values: >=0

Description The text of a bar code found on a page.

Value Type: TW_HANDLE

Allowed Values: Any handle to a string


TWEI_BARCODEX

TWEI_BARCODEY

TWEI_BARCODETYPE

Shaded Area Detection and Removal

TWEI_DESHADECOUNT

TWEI_DESHADETOP

TWEI_DESHADELEFT

Description The X coordinate of a bar code found on a page.


Allowed Values: >=0

Description The Y coordinate of a bar code found on a page.


Allowed Values: >=0

Description The type of bar code found on a page.


Allowed Values: TWBT_3OF9

Description Returns the number of shaded regions found and erased in the document image. A value of 0 means the deshade engine was enabled but that no regions were processed. A value of -1 means the deshade engine was not enabled.


Allowed Values: >=0

Description The top coordinate of a shaded region found on a page.


Allowed Values: >=0

Description The left coordinate of a shaded region found on a page.


Allowed Values: >=0


Chapter 9

TWEI_DESHADEHEIGHT

TWEI_DESHADEWIDTH

TWEI_DESHADESIZE

TWEI_DESHADEBLACKCOUNTOLD

TWEI_DESHADEBLACKCOUNTNEW

TWEI_DESHADEBLACKRLMIN

Description The height of a shaded region found on a page.


Allowed Values: >=0

Description The width of a shaded region found on a page.


Allowed Values: >=0

Description The width of the dots within the shade region.


Allowed Values: >=0

Description The total number of black pixels in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The total number of black pixels in the region after deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The shortest black pixel run-length in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0


TWEI_DESHADEBLACKRLMAX

TWEI_DESHADEWHITECOUNTOLD

TWEI_DESHADEWHITECOUNTNEW

TWEI_DESHADEWHITERLMIN

TWEI_DESHADEWHITERLAVE

TWEI_DESHADEWHITERLMAX

Speckle Removal

Description The longest black pixel run-length in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The total number of white pixels in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The total number of white pixels in the region after deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The shortest white pixel run-length in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The average length of all white pixel run-lengths in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0

Description The longest white pixel run-length in the region prior to deshading. If this value is unknown the Source returns -1.


Allowed Values: >=0


Chapter 9

TWEI_SPECKLESREMOVED

TWEI_BLACKSPECKLESREMOVED

TWEI_WHITESPECKLESREMOVED

Horizontal Line Detection and Removal

TWEI_HORZLINECOUNT

TWEI_HORZLINEXCOORD

TWEI_HORZLINEYCOORD

Description The number of speckles removed from the image when de-speckle is enabled.


Allowed Values: >=0

Description The number of black speckles removed from the image when despeckle is enabled.


Allowed Values: >=0

Description The number of white speckles removed (black speckles added) from the image when despeckle is enabled.


Allowed Values: >=0

Description Returns the number of horizontal lines found and erased in the document image. A value of 0 means the line removal engine was enabled but that no lines were found. A value of -1 means the line engine was not enabled.


Allowed Values: >=0

Description The x coordinate of a horizontal line detected in the image.


Allowed Values: >=0

Description The y coordinate of a horizontal line detected in the image


Allowed Values: >=0


TWEI_HORZLINELENGTH

TWEI_HORZLINETHICKNESS

Vertical Line Detection and Removal

TWEI_VERTLINECOUNT

TWEI_VERTLINEXCOORD

Description The length of a horizontal line detected in the image.


Allowed Values: >=0

Description The thickness (height) of a horizontal line detected in the image.


Allowed Values: >=0

Description Returns the number of vertical lines found and erased in the document image. A value of 0 means the line removal engine was enabled but that no lines were found. A value of -1 means the line engine was not enabled.


Allowed Values: >=0

Description The x coordinate of a vertical line detected in the image.


Allowed Values: >=0


Chapter 9

TWEI_VERTLINEYCOORD

TWEI_VERTLINELENGTH

TWEI_VERTLINETHICKNESS

Patch Code Detection (Job Separation)

TWEI_PATCHCODE

Skew detection and Removal

TWEI_DESKEWSTATUS

TWEI_SKEWORIGINALANGLE

Description The y coordinate of a vertical line detected in the image.


Allowed Values: >=0

Description The length of a vertical line detected in the image.


Allowed Values: >=0

Description The thickness (width) of a vertical line detected in the image.


Allowed Values: >=0

Description The patch code detected.


Allowed Values: TWPCH_PATCH1, TWPCH_PATCH2, TWPCH_PATCH3, TWPCH_PATCH4, TWP= CH_PATCH6, TWPCH_PATCHT

Description Returns the status of the deskew operation.


Allowed Values: TWDSK_SUCCESS Image successfully deskewedTWDSK_REPORTONLY Deskew information onlyTWDSK_FAIL Deskew failedTWDSK_DISABLED Deskew engine not enabled

Description The amount of skew in the original image.


Allowed Values: >=0


TWEI_SKEWFINALANGLE

TWEI_SKEWCONFIDENCE

TWEI_SKEWWINDOWX1

TWEI_SKEWWINDOWY1

TWEI_SKEWWINDOWX2

Description The amount of skew in the deskewed image. This number may not be zero.


Allowed Values: >=0

Description This number reflects the degree of certainty the deskew engine has in the accuracy of the deskewing of the current image and ranges from 0 (no confidence) to 100 (supreme confidence). The Source may return a value of -1 if it does not support confidence reporting.


Allowed Values: >=0

Description This is the X image coordinate of the upper left corner of the virtual deskewed image. It may be negative indicating the deskewed corner is not represented by actual pixels.


Allowed Values: >=0

Description The Y image coordinate of the upper left corner of the virtual deskewed image. It may be negative indicating the deskewed corner is not represented by actual pixels.


Allowed Values: >=0

Description The X image coordinate of the upper right corner of the virtual deskewed image.


Allowed Values: >=0


Chapter 9

TWEI_SKEWWINDOWY2

TWEI_SKEWWINDOWX3

TWEI_SKEWWINDOWY3

TWEI_SKEWWINDOWX4

TWEI_SKEWWINDOWY4

Endorsed / Imprinted Text

TWEI_ENDORSEDTEXT

Description The Y image coordinate of the upper right corner of the virtual deskewed image.


Allowed Values: >=0

Description This is the X image coordinate of the lower left corner of the virtual deskewed image. It may be negative indicating the deskewed corner is not represented by actual pixels.


Allowed Values: >=0

Description The Y image coordinate of the lower left corner of the virtual deskewed image.


Allowed Values: >=0

Description The X image coordinate of the lower right corner of the virtual deskewed image.


Allowed Values: >=0

Description The Y image coordinate of the lower right corner of the deskewed image.


Allowed Values: >=0

Description The text that was endorsed on the paper by the scanner.

Value Type: TW_STR255

Allowed Values: Any string


Forms Recognition

TWEI_FORMCONFIDENCE

TWEI_FORMTEMPLATEMATCH

TWEI_FORMTEMPLATEPAGEMATCH

TWEI_FORMHORZDOCOFFSET

TWEI_FORMVERTDOCOFFSET

Description The confidence that the specified form was detected. This is an array property with a confidence factor for each form In the data set with 0 meaning no match and 100 meaning absolute certainty. Typically values over 70 imply a good form match with the template.


Allowed Values: 0 to 100

Description The array of file names for the master forms matched against a form. If multi-page master forms are used, the associated page numbers are contained in the FORMTEMPLATEPAGEMATCH capability array.



Description An array containing the number of the page from a multi-page master form matched against a form image. It is useful when matching a form image against the pages of a multi-page master form. The file name of the master form is contained in the FORMTEMPLATEMATCH capability.


Allowed Values: >=0

Description An array containing the perceived horizontal offsets of the form image being matched against a set of master forms. This is useful for page registration once the form has been recognized.


Allowed Values: >=0

Description An array containing the perceived vertical offsets of the form image being matched against a set of master forms. This is useful for page registration once the form has been recognized.


Allowed Values: >= 0


Chapter 9

TWAIN 1.9 Extended Image Attribute CapabilitiesThese next items, taken together, provide a way to unambiguously identify the physical source of an image. Applications can use this information to associate scanned images from the same side of a sheet of paper, the sheet of paper itself, or a set of sheets comprising a document. While much of this information is available using DAT_IMAGELAYOUT, it is provided here for performance reasons; to allow an Application to glean as much information about the image as possible through a single call.

These items are mandatory, if a Source supports DAT_EXTIMAGEINFO, then these items must be present in the data returned by the Source.


TWEI_BOOKNAME

TWEI_CHAPTERNUMBER

TWEI_DOCUMENTNUMBER

Description This is new with TWAIN 1.9, expanding on the document/page/frame numbers described by previous versions of TWAIN in the TW_IMAGELAYOUT structure. The ordering is book/chapter/document/page(camera)/frame, and increases the detail of image addressing that a Source can provide for an Application. TWAIN 1.9 Sources that support extended image info must provide this information, even if the value is always fixed at 1.


Allowed Values: Any valid string data.

See Also: DAT_IMAGELAYOUTTW_IMAGELAYOUT

Description This is new with TWAIN 1.9, expanding on the document/page/frame numbers described by previous versions of TWAIN in the TW_IMAGELAYOUT structure. The ordering is book/chapter/document/page(camera)/frame, and increases the detail of image addressing that a Source can provide for an Application. TWAIN 1.9 Sources that support extended image info must provide this information, even if the value is always fixed at 1.


Allowed Values: 1 to 232-1


Description This must be the same value returned by a call to DG_CONTROL / DAT_IMAGELAYOUT / MSG_GET. The ordering is book/chapter/document/page(camera)/frame, and increases the amount of image addressing that a Source can provide for an Application. TWAIN 1.9 Sources that support extended image info must provide this information, even if the value is always fixed at 1.





Chapter 9

TWEI_PAGENUMBER

TWEI_CAMERA

Description This must be the same value returned by a call to DG_CONTROL / DAT_IMAGELAYOUT / MSG_GET. The ordering is book/chapter/document/page(camera)/frame, and increases the amount of image addressing that a Source can provide for an Application. TWAIN 1.9 Sources that support extended image info must provide this information, even if the value is always fixed at 1.




Description The primary use of this value is to determine if the image is from the top or the bottom side of a sheet of paper. This is accomplished by naming the camera that was used to obtain the image. For Sources that support DAT_FILESYSTEM, the Application can use the string to determine if the camera is capturing images from the top or bottom side of the paper.Applications should browse the available camera devices in State 4 to create a lookup table mapping the various camera filenames to the side they represent. DAT_FILESYSTEM is not supported, then the Application should watch for the strings “TOP” and “BOTTOM”.


Allowed Values: TWFY_CAMERA, TWFY_CAMERATOP and TWFY_CAMERABOTTOM filenames maintained by the Source and accessible using the DAT_FILESYSTEM triplet. This string must be exactly the same as that supplied by the Source when the Application issues a DAT_FILESYSTEM / MSG_GETINFO (or related command). The Source must identify the exact camera used. This means that even if the Source has been set to use a TWFY_CAMERA device, it must report the TWFY_CAMERATOP or TWFY_CAMERABOTTOM device as appropriate.If the Source does not support the use of DAT_FILESYSTEM, then it must return the string “TOP” for images from the top side of the sheet of paper, and “BOTTOM” for images on the bottom side of the sheet of paper.


TWEI_FRAMENUMBER

Description This must be the same value returned by a call to DG_CONTROL / DAT_IMAGELAYOUT / MSG_GET. TWAIN 1.9 Sources that support extended image info must provide this information.





Chapter 9

TWEI_FRAME

TWEI_PIXELFLAVOR

TWAIN 1.91 Extended Image Attribute CapabilitiesThese next items add image segmentation and ICC Profile metadata returns.

Description Returns the coordinates of the current segment within the current document in pixels. Since segments may be acquired at various resolutions, the physical location must be calculated using the resolution reported by DAT_IMAGEINFO for the current segment. The top left coordinate stored in the FRAME is relative to the top left of the scanned document.

Value Type: TW_FRAME

Allowed Values: Any valid FRAME describing a segment within the boundaries of the current document

See Also: TWEI_SEGMENTNUMBER

DAT_IMAGELAYOUTTW_IMAGELAYOUTICAP_FRAMES

Description This value must correctly describe the pixel flavor of the current image, the same data that is available through ICAP_PIXELFLAVOR. TWAIN 1.9 Sources that support extended image info must provide this information.


Allowed Values: TWPF_CHOCOLATETWPF_VANILLA

See Also: ICAP_PIXELFLAVOR


TWEI_ICCPROFILE

TWEI_LASTSEGMENT

TWEI_SEGMENTNUMBER

TWAIN 2.0 Extended Image Attribute CapabilitiesThese next items provide support for MICR.

Description Returns the name of the ICC profile that was used to render the current image. This may be a fully qualified path indicating the exact location of the ICC profile.If this is not a fully qualified path, then the default location is operating system dependant. Windows default location: <windows path>\system32\spool


Allowed Values: Any valid ICC profile file name or fully qualified path

Description Returns TRUE if the current segment is the last segment of a page.

Value Type: TW_BOOL

Allowed Values: TRUE or FALSE

See Also:

Description Returns a number identifying the segment of an image. Segments allow independent image processing strategies on a document for more accurate document reproduction and smaller file sizes. For instance, a document containing text with a picture may be segmented into a high resolution bitonal image consisting of the text and a lower resolution color image consisting of the picture. Sources that support this item must support TWEI_FRAME, and must specify a left and top value to position the segment in the final image. Segments may overlap.


Allowed Values: >=0

See Also: TWEI_FRAMEDAT_IMAGELAYOUTTW_IMAGELAYOUTICAP_FRAMES


Chapter 9

MICR Types

TWMD_MICR

Reports back that magnetic data was found and it is of a string. Data may contain placeholders for unrecognized characters.

TWMD_RAW

Reports back the raw magnetic data that was read.

TWMD_INVALID

Reports back that magnetic data was found, but it is not in a valid MICR format


TWAIN 2.1 Extended Image Attribute CapabilitiesTWEI_FILESYSTEMSOURCE

TWEI_IMAGEMERGED

TWEI_MAGDATA

TWEI_MAGDATALENGTH

TWEI_MAGTYPE

Description Returns a DAT_FILESYSTEM string describing the camera that captured the image data.


Allowed Values: Any of the camera values returned by DAT_FILESYSTEM / MSG_GETFIRSTFILE or MSG_GETNEXTFILE

Description Indicates that the current image is the result of a merger between the front and rear images of a duplex capture. See CAP_IMAGEMERGE for more information.

Value Type: TW_BOOL

Allowed Values: TRUE if the front and rear images were merged.

Description This is a “blob” of data with a byte count retrieved from the driver/device. The interpretation of the data comes from TWEI_MAGTYPE.

Value Type: TW_HANDLE, or TW_STR255

Allowed Values: Any handle to a blob of data

Description: This describes the length of the magnetic data. Either in bytes for “blob” or data or characters for string data.


Allowed Values: >=0

Description This describes the kind of magnetic data.


Allowed Values: TWMD_MICR, TWMD_RAW, or TWMD_INVALID


Chapter 9

TWEI_PAGESIDE

Description Returns a value indicating if the image represents the front or rear of the sheet of paper.


Allowed Values: TWCS_TOP (front of sheet)TWCS_BOTTOM (rear of sheet)


10Capabilities

Chapter ContentsOverview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-1Required Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2Capabilities in Categories of Functionality . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-2The Capability Listings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10-10

OverviewSources may support a large number of capabilities but are required to support very few. To determine if a capability is supported by a Source, the application can query the Source using a DG_CONTROL / DAT_CAPABILITY / MSG_GET, MSG_GETCURRENT, or MSG_GETDEFAULT operation. The application specifies the particular capability by storing its identifier in the Cap field of the TW_CAPABILITY structure. This is the structure pointed to by the pData parameter in the DSM_Entry( ) call.

DG_CONTROL / DAT_CAPABILITY operations for capability negotiation include:

MSG_GET Returns the available settings for this capability, as well as the Current and Default settings (if the container is TW_ENUMERATION or TW_RANGE).

MSG_GETCURRENT Returns the Current setting for this capability.

MSG_GETDEFAULT Returns the value of the Source’s preferred Default values.

MSG_RESET Returns the capability to its TWAIN Default (power-on) condition (i.e. all previous negotiation is ignored).

MSG_RESETALL Returns all of the current values to the default settings used when the driver was first installed.

MSG_SET Allows the application to set the Current value of a capability or even to restrict the available values to some subset of the Source’s power-on set of values. Sources are strongly encouraged to allow the application to set as many of its capabilities as possible, and further to reflect these changes in the Source’s user interface. This will


Chapter 10

ensure that the user can only select images with characteristics that are useful to the consuming application.

Required CapabilitiesThe list of required capabilities can be found in Chapter 5, "Source Implementation.”

Sources must implement and make available to TWAIN applications the advertised features of the devices they support. This is especially true in “no-UI mode.” A Source must support a capability if its device supports it, even if the capability is listed as required by none.

Capabilities in Categories of Functionality

Asynchronous Device Events

Audible Alarms

Audio

Automatic Adjustments

CAP_DEVICEEVENT MSG_SET selects which events the application wants the source to report; MSG_RESET returns the preferred settings of the source.

CAP_ALARMS Turns specific audible alarms on and off.

CAP_ALARMVOLUME Controls the volume of a device’s audible alarm.

ACAP_XFERMECH Allows application and source to identify which audio transfer mechanisms they have in common.

CAP_AUTOMATICSENSEMEDIUM Configures a Source to check for paper in the Automatic Document Feeder.

ICAP_AUTODISCARDBLANKPAGES Discards blank pages.

ICAP_AUTOMATICBORDERDETECTION Turns automatic border detection on and off.

ICAP_AUTOMATICCOLORENABLED Detects the pixel type of the image and returns either a color image or a non-color image specified by ICAP_AUTOMATICCOLORNONCOLORPIXELTYPE.


Automatic Capture

Automatic Scanning

ICAP_AUTOMATICCOLORNONCOLORPIXELTYPE Specifies the non-color pixel type to use when automatic color is enabled.

ICAP_AUTOMATICCROPUSESFRAME Reduces the amount of data captured from the device, potentially improving the performance of the driver.

ICAP_AUTOMATICDESKEW Turns automatic skew correction on and off.

ICAP_AUTOMATICLENGTHDETECTION Controls the automatic detection of the length of a document, this is intended for use with an Automatic Document Feeder.

ICAP_AUTOMATICROTATE When TRUE, depends on source to automatically rotate the image.

ICAP_AUTOSIZE Force the output image dimensions to match either the current value of ICAP_SUPPORTEDSIZES or any of its current allowed values.

ICAP_FLIPROTATION Orients images that flip orientation every other image.

ICAP_IMAGEMERGE Merges the front and rear image of a document in one of four orientations: front on the top.

ICAP_IMAGEMERGEHEIGHTTHRESHOLD Specifies a Y-Offset in ICAP_UNITS units.

CAP_AUTOMATICCAPTURE Specifies the number of images to automatically capture.

CAP_TIMEBEFOREFIRSTCAPTURE Selects the number of seconds before the first picture taken.

CAP_TIMEBETWEENCAPTURES Selects the hundredths of a second to wait between pictures taken.

CAP_AUTOSCAN Enables the source’s automatic document scanning process.

CAP_CAMERAENABLED Delivers images from the current camera.

CAP_CAMERAORDER Selects the order of output for Single Document Multiple Image mode.

CAP_CAMERASIDE Sets the top and bottom values of cameras in a scanning device.

CAP_CLEARBUFFERS MSG_GET reports presence of data in scanner’s buffers; MSG_SET clears the buffers.

CAP_MAXBATCHBUFFERS Describes the number of pages that the scanner can buffer when CAP_AUTOSCAN is enabled.


Chapter 10

Bar Code Detection Search Parameters

Capability Negotiation Parameters

Color

Compression

ICAP_BARCODEDETECTIONENABLED Turns bar code detection on and off.

ICAP_SUPPORTEDBARCODETYPES Provides a list of bar code types that can be detected by current data source.

ICAP_BARCODEMAXRETRIES Restricts the number of times a search will be retried if no bar codes are found.

ICAP_BARCODEMAXSEARCHPRIORITIES Specifies the maximum number of supported search priorities.

ICAP_BARCODESEARCHMODE Restricts bar code searching to certain orientations, or prioritizes one orientation over another.

ICAP_BARCODESEARCHPRIORITIES A prioritized list of bar code types dictating the order in which they will be sought.

ICAP_BARCODETIMEOUT Restricts the total time spent on searching for bar codes on a page.

CAP_EXTENDEDCAPS Capabilities negotiated in States 5 & 6

CAP_SUPPORTEDCAPS Inquire Source’s capabilities valid for MSG_GET

ICAP_COLORMANAGEMENTENABLED Disables the Source’s color and gamma tables for color and grayscale images, resulting in output that that could be termed “raw”.

ICAP_FILTER Color characteristics of the subtractive filter applied to the image data

ICAP_GAMMA Gamma correction value for the image data

ICAP_ICCPROFILE Embeds or links ICC profiles into files

ICAP_PLANARCHUNKY Color data format - Planar or Chunky

ICAP_BITORDERCODES CCITT Compression

ICAP_CCITTKFACTOR CCITT Compression

ICAP_COMPRESSION Compression method for Buffered Memory Transfers

ICAP_JPEGPIXELTYPE JPEG Compression

ICAP_JPEGQUALITY JPEG quality


Device Parameters

Imprinter/Endorser Functionality

ICAP_PIXELFLAVORCODES CCITT Compression

ICAP_TIMEFILL CCITT Compression

CAP_DEVICEONLINE Determines if hardware is on and ready

CAP_DEVICETIMEDATE Date and time of a device’s clock.

CAP_SERIALNUMBER The serial number of the currently selected source device.

ICAP_MINIMUMHEIGHT Allows the source to define the minimum height (Y-axis) that the source can acquire.

ICAP_MINIMUMWIDTH Allows the source to define the minimum width (X-axis) that the source can acquire.

ICAP_EXPOSURETIME Exposure time used to capture the image, in seconds

ICAP_FLASHUSED2 For devices that support a flash, MSG_SET selects the flash to be used; MSG_GET reports the current setting.

ICAP_IMAGEFILTER For devices that support image filtering, selects the algorithm to be used.

ICAP_LAMPSTATE Is the lamp on?

ICAP_LIGHTPATH Image was captured transmissively or reflectively

ICAP_LIGHTSOURCE Describes the color characteristic of the light source used to acquire the image

ICAP_NOISEFILTER For devices that support noise filtering, selects the algorithm to be used.

ICAP_OVERSCAN For devices that support overscanning, controls whether additional rows or columns are appended to the image.

ICAP_PHYSICALHEIGHT Maximum height Source can acquire (in ICAP_UNITS)

ICAP_PHYSICALWIDTH Maximum width Source can acquire (in ICAP_UNITS)

ICAP_UNITS Unit of measure (inches, centimeters, etc.)

ICAP_ZOOMFACTOR With MSG_GET, returns all camera supported lens zooming range.

CAP_ENDORSER Allows the application to specify the starting endorser / imprinter number.

CAP_PRINTER MSG_GET returns current list of available printer devices; MSG_SET selects the device for negotiation.

CAP_PRINTERENABLED Turns the current CAP_PRINTER device on or off.

CAP_PRINTERINDEX Starting number for the CAP_PRINTER device.


Chapter 10

Image Information

Image Parameters for Acquire

Image Type

CAP_PRINTERMODE Specifies appropriate current CAP_PRINTER device mode.

CAP_PRINTERSTRING String(s) to be used in the string component when CAP_PRINTER device is enabled.

CAP_PRINTERSUFFIX String to be used as current CAP_PRINTER device’s suffix.

CAP_AUTHOR Author of acquired image (may include a copyright string)

CAP_CAPTION General note about acquired image

CAP_TIMEDATE Date and Time the image was acquired (entered State 7)

ICAP_EXTIMAGEINFO Allows the application to query the data source to see if it supports the new operation triplet DG_IMAGE/ DAT_EXTIMAGEINFO/ MSG_GET.

ICAP_SUPPORTEDEXTIMAGEINFO Lists all of the information that the Source is capable of returning from a call to DAT_EXTIMAGEINFO.

CAP_THUMBNAILSENABLED Allows an application to request the delivery of thumbnail representations for the set of images that are to be delivered.

ICAP_AUTOBRIGHT Enable Source’s Auto-brightness function

ICAP_BRIGHTNESS Source brightness values

ICAP_CONTRAST Source contrast values

ICAP_HIGHLIGHT Lightest highlight, values lighter than this value will be set to this value

ICAP_IMAGEDATASET Gets or sets the image indices that will be delivered during the standard image transfer done in States 6 and 7.

ICAP_ORIENTATION Defines which edge of the paper is the top: Portrait or Landscape

ICAP_ROTATION Source can, or should, rotate image this number of degrees

ICAP_SHADOW Darkest shadow, values darker than this value will be set to this value

ICAP_XSCALING Source Scaling value (1.0 = 100%) for x-axis

ICAP_YSCALING Source Scaling value (1.0 = 100%) for y-axis

ICAP_BITDEPTH Pixel bit depth for Current value of ICAP_PIXELTYPE


Language Support

MICR

Pages

Paper Handling

ICAP_BITDEPTHREDUCTION Allows a choice of the reduction method for bit depth loss

ICAP_BITORDER Specifies how the bytes in an image are filled by the Source

ICAP_CUSTHALFTONE Square-cell halftone (dithering) matrix to be used

ICAP_HALFTONES Source halftone patterns

ICAP_PIXELFLAVOR Sense of the pixel whose numeric value is zero

ICAP_PIXELTYPE The type of pixel data (B/W, gray, color, etc.)

ICAP_THRESHOLD Specifies the dividing line between black and white values

CAP_LANGUAGE Allows application and source to identify which languages they have in common.

CAP_MICRENABLED Enables actions needed to support check scanning.

CAP_SEGMENTED Describes the segmentation setting for captured images

ICAP_FRAMES Size and location of frames on page

ICAP_MAXFRAMES Maximum number of frames possible per page

ICAP_SUPPORTEDSIZES Fixed frame sizes for typical page sizes

CAP_AUTOFEED MSG_SET to TRUE to enable Source’s automatic feeding

CAP_CLEARPAGE MSG_SET to TRUE to eject current page and leave acquire area empty

CAP_DUPLEX Indicates whether the scanner supports duplex.

CAP_DUPLEXENABLED Enables the user to set the duplex option to be TRUE or FALSE.

CAP_FEEDERALIGNMENT If TRUE, feeder is centered; FALSE if it is free-floating.

CAP_FEEDERENABLED If TRUE, Source’s feeder is available

CAP_FEEDERLOADED If TRUE, Source has documents loaded in feeder (MSG_GET only)


Chapter 10

Patch Code Detection

Power Monitoring

CAP_FEEDERORDER Specifies whether feeder starts with top of first or last page.

CAP_FEEDERPOCKET Report what pockets are available as paper leaves a device.

CAP_FEEDERPREP Improve the movement of paper through a scanner ADF.

CAP_FEEDPAGE MSG_SET to TRUE to eject current page and feed next page

CAP_PAPERDETECTABLE Determines whether source can detect documents on the ADF or flatbed.

CAP_REACQUIREALLOWED Capable of acquring muliple images of the same page wihtout changing the physical registraion of that page.

CAP_REWINDPAGE MSG_SET to TRUE to do a reverse feed

ICAP_FEEDERTYPE Allows application to set scan parameters depending on the type of feeder being used.

ICAP_PATCHCODEDETECTIONENABLED Turns patch code detection on and off.

ICAP_SUPPORTEDPATCHCODETYPES List of patch code types that can be detected by current data source.

ICAP_PATCHCODEMAXSEARCHPRIORITIES Maximum number of search priorities.

ICAP_PATCHCODESEARCHPRIORITIES List of patch code types dictating the order in which patch codes will be sought.

ICAP_PATCHCODESEARCHMODE Restricts patch code searching to certain orientations, or prioritizes one orientation over another.

ICAP_PATCHCODEMAXRETRIES Restricts the number of times a search will be retried if none are found on a page.

ICAP_PATCHCODETIMEOUT Restricts total time for searching for a patch code on a page.

CAP_BATTERYMINUTES The minutes of battery power remaining on a device.

CAP_BATTERYPERCENTAGE With MSG_GET, indicates battery power status.

CAP_POWERSAVETIME With MSG_SET, sets the camera power down timer in seconds; with MSG_GET, returns the current setting of the power down time.

CAP_POWERSUPPLY MSG_GET reports the kinds of power available; MSG_GETCURRENT reports the current power supply to use.


Resolution

Transfers

User Interface

ICAP_XNATIVERESOLUTION Native optical resolution of device for x-axis

ICAP_XRESOLUTION Current/Available optical resolutions for x-axis

ICAP_YNATIVERESOLUTION Native optical resolution of device for y-axis

ICAP_YRESOLUTION Current/Available optical resolutions for y-axis

CAP_JOBCONTROL Allows multiple jobs in batch mode.

CAP_XFERCOUNT Number of images the application is willing to accept this session

ICAP_COMPRESSION Buffered Memory transfer compression schemes

ICAP_IMAGEFILEFORMAT File formats for file transfers

ICAP_TILES Tiled image data

ICAP_UNDEFINEDIMAGESIZE The application will accept undefined image size

ICAP_XFERMECH Transfer mechanism - used to learn options and set-up for upcoming transfer

CAP_CAMERAPREVIEWUI Queries the source for UI support for preview mode.

CAP_CUSTOMDSDATA Allows the application to query the data source to see if it supports the new operation triplets DG_CONTROL/ DAT_CUSTOMDSDATA / MSG_GET and DG_CONTROL/ DAT_CUSTOMDSDATA / MSG_SET.

CAP_CUSTOMINTERFACEGUID Uniquely identifies an interface for a Data Source.

CAP_ENABLEDSUIONLY Queries an application to see if it implements the new user interface settings dialog.

CAP_INDICATORS Use the Source’s progress indicator? (valid only when ShowUI==FALSE)

CAP_UICONTROLLABLE Indicates that Source supports acquisitions with UI disabled


Chapter 10

The Capability ListingsThe following section lists descriptions of all TWAIN capabilities in alphabetical order. The format of each capability entry is:

NAME OF CAPABILITY

Description

Description of the capability

Application

(Optional) Information for the application

Source

(Optional) Information for the Source

Values

Type: Data structure for the capability.

Default Value: The value the Source must use as the Current value when entering State 4 (following DG_CONTROL / DAT_IDENTITY / MSG_OPENDS).

This is the value the Source resets the Current value to when it receives a MSG_RESET operation.

The Source reports its preferred Default value when it receives a MSG_GETDEFAULT. The Source’s preferred value may be different from the TWAIN Default value.

Allowed Values: Definition of the values allowed for this capability.

Container for MSG_GET Acceptable containers for use on MSG_GET operations.

Container for MSG_SET Acceptable containers for use on MSG_SET operations.

Required By

If a Source or application is required to support the capability.

Source Required Operations

Operations the Source is required to support.

See Also

Associated capabilities and data structures.


ACAP_XFERMECH

Description

Allows the Application and Source to identify which audio transfer mechanisms they have in common.

Application

The current setting of ACAP_XFERMECH must match the constant used by the application to specify the audio transfer mechanism when starting the transfer using the triplet: DG_AUDIO / DAT_AUDIOxxxxXFER / MSG_GET.

Values

Type: TW_UINT16

Default Value: TWSX_NATIVE

Allowed Values: TWSX_NATIVETWSX_FILETWSX_FILE2

Container for MSG_GET: TW_ENUMERATIONTW_ONEVALUE

Container for MSG_SET: TW_ENUMERATIONTW_ONEVALUE

Container for MSG_QUERYSUPPORT: TW_ONEVALUE

Required By

All Audio Sources


MSG_GET/CURRENT/DEFAULT,MSG_SET/RESET

See Also

DG_AUDIO / DAT_AUDIOxxxxXFER / MSG_GET


Chapter 10

CAP_ALARMS

Description

Turns specific audible alarms on and off.

Application

Note that an application may opt to turn off all alarms by issuing a MSG_SET with no data. Therefore, an application should also be prepared to receive an empty array from a Source with an MSG_GET. (i.e., pTW_ARRAY->NumItems == 0)

The easiest way to test for allowed values is to try to set them all with MSG_SET. If not all are allowed, the Source will return TWRC_CHECKSTATUS with those values that it supports.

Source

It is worth noting that the alarms do not have to be present in the device for a Source to make use of this capability. If the device is capable of alerting the Source to these various kinds of conditions, but is unable to generate the alarms, itself; then the Source may opt to generate them on its behalf.

TWAL_ALARM is a catchall for alarms not explicitly listed. It is also used where a device only provides control over a single, multi-use alarm. For instance, if a device beeps for both jams and bar-codes, but doesn’t allow independent control of the alarms, then it should report TWAL_ALARM to cover them, and not TWAL_BARCODE, TWAL_JAM.

TWAL_FEEDERERROR covers paper handling errors such as jams, double-feeds, skewing and the like; conditions that most likely stop scanning.

TWAL_FEEDERWARNING covers non-fatal events, such as feeder empty.

TWAL_DOUBLEFEED, TWAL_JAM and TWALSKEW cover paper handling errors.

TWAL_BARCODE and TWAL_PATCHCODE generate alarms when an image with this kind of data is recognized.

TWAL_POWER generates alarms for any changes in power to the device.

If not supported, return TWRC_FAILURE / TWCC_CAPUNSUPPORTED.

If Operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CONTROL /DAT_CAPABILITY/ MSG_QUERYSUPPORT)

Values

Type: TW_UINT16

Default Value: No default

Allowed Values: TWAL_ALARMTWAL_FEEDERERRORTWAL_FEEDERWARNING


TWAL_BARCODETWAL_DOUBLEFEEDTWAL_JAMTWAL_PATCHCODETWAL_POWERTWAL_SKEW

Container for MSG_GET: TW_ARRAY

Container for MSG_SET: TW_ARRAY


Required By

None


None

See Also

CAP_ALARMVOLUME


Chapter 10

CAP_ALARMVOLUME

Description

The volume of a device’s audible alarm. Note that this control affects the volume of all alarms; no specific volume control for individual types of alarms is provided.

Application

Take note of the range step, some Sources may only offer a step of 100, which turns the alarm on or off.

Source

If 0, the audible alarm is turned off. All other values control the volume of the alarm.

Windows only - If the alarm is managed in the Source, as opposed to the device, then it should be consistent with the control panel Accessibility Options (i.e., the user should get visual notification if that is the current setting for the desktop).



Values

Type: TW_INT32


Allowed Values: 0 - 100

Container for MSG_GET: TW_ONEVALUE,TW_RANGE

Container for MSG_SET: TW_ONEVALUE,TW_RANGE


Required By

None


None

See Also

CAP_ALARMS


CAP_AUTHOR

Description

The name or other identifying information about the Author of the image. It may include a copyright string.

Source


Values

Type: TW_STR128

Default Value: “\0”


Container for MSG_GET: TW_ONEVALUE

Container for MSG_SET: TW_ONEVALUE


Required By

None


None

See Also

CAP_CAPTIONCAP_TIMEDATE


Chapter 10

CAP_AUTOFEED

Description

If TRUE, the Source will automatically feed the next page from the document feeder after the number of frames negotiated for capture from each page are acquired. CAP_FEEDERENABLED must be TRUE to use this capability.

Application

Set the capability to TRUE to enable the Source’s automatic feed process, or FALSE to disable it. After the completion of each transfer, check TW_PENDINGXFERS. Count to determine if the Source has more images to transfer. A -1 means there are more images to transfer but the exact number is not known.

CAP_FEEDERLOADED indicates whether the Source’s feeder is loaded. (The automatic feed process continues whenever this capability is TRUE.)

Source

If CAP_FEEDERENABLED equals FALSE, return TWRC_FAILURE / TWCC_CAPUNSUPPORTED (capability is not supported in current settings).

If it is supported, return TWRC_SUCCESS and enable the device’s automatic feed process: After all frames negotiated for capture from each page are acquired, put the current document in the output area and advance the next document from the input area to the feeder image acquisition area. If the feeder input area is empty, the automatic feeding process is suspended but should continue when the feeder is reloaded.

Values

Type: TW_BOOL

Default Value: No Default


Container for MSG_GET: TW_ONEVALUE,TW_ENUMERATION // 2.0 and higher

Container for MSG_SET: TW_ONEVALUE,TW_ENUMERATION // 2.0 and higher


Required By

All Sources with Feeder Devices




See Also

CAP_CLEARPAGECAP_FEEDERENABLEDCAP_FEEDERLOADEDCAP_FEEDPAGECAP_REWINDPAGE


Chapter 10

CAP_AUTOMATICCAPTURE

Description

The number of images to automatically capture. This does not refer to the number of images to be sent to the Application, use CAP_XFERCOUNT for that.

Source

If 0, Automatic Capture is disabled If 1 or greater, that number of images is captured by the device.

Automatic capture implies that the device is capable of capturing images without the presence of the Application. This means that it must be possible for the Application to close the Source and reopen it later, after the images have been captured.



Values

Type: TW_INT32

Default Value: 0

Allowed Values: 0 or greater




Required By

None


None

See Also

CAP_TIMEBEFOREFIRSTCAPTURECAP_TIMEBETWEENCAPTURESCAP_XFERCOUNT

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORY


CAP_AUTOMATICSENSEMEDIUM

Description

Configures a Source to check for paper in the Automatic Document Feeder, and if it finds any, then automatically capture all of its images from the Feeder. If the Feeder is empty when acquisition starts, then all images are automatically captured from the Flatbed.

Application

This capability offers a less complex method to let the Source automatically choose whether to acquire images from the Automatic Document Feeder or from the Flatbed.

Note: If this capability is not supported, Applications can simulate this behavior by examining CAP_FEEDERLOADED. If it is TRUE, set CAP_FEEDERENABLED to TRUE. If it is FALSE, set CAP_FEEDERENABLED to FALSE. And after that begin to acquire images.

Source

If the Source supports CAP_PAPERDETECTABLE, and it has both an Automatic Document Feeder and a Flatbed, then it should support this capability.

When this capability is set to TRUE the Source ignores the value of CAP_FEEDERENABLED. It always attempts to acquire its first image from the Automatic Document Feeder. If paper is not present, then images are acquired from the Flatbed.

When this capability is set to FALSE the source of images is determined by CAP_FEEDERENABLED.

Values

Type: TW_BOOL

Default Value: FALSE

Allowed Values: TRUE, FALSE

Container for MSG_GET: TW_ONEVALUE , TW_ENUMERATION

Container for MSG_GET: TW_ONEVALUE , TW_ENUMERATION


Required By

None

Source Operations

MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, MSG_QUERYSUPPORT, MSG_RESET, MSG_SET


Chapter 10

See Also

CAP_FEEDERENABLED, CAP_FEEDERLOADED


CAP_AUTOSCAN

Description

This capability is intended to boost the performance of a Source. The fundamental assumption behind AutoScan is that the device is able to capture the number of images indicated by the value of CAP_XFERCOUNT without waiting for the Application to request the image transfers. This is only possible if the device has internal buffers capable of caching the images it captures.

The default behavior is undefined, because some high volume devices are incapable of anything but CAP_AUTOSCAN being equal to TRUE. However, if a Source supports FALSE, it should use it as the mandatory default, since this best describes the behavior of pre-1.8 TWAIN Applications.

Application

The application should check the TW_PENDINGXFERS.Count, and continue to scan until it becomes 0.

When AutoScan is set to TRUE, the Application should not rely on just the paper sensors (for example, CAP_FEEDERLOADED) to determine if there are images to be transferred. The latency between the Source and the Application makes it very likely that at the time the sensor reports FALSE, there may be more than one image waiting for the transfer inside of the device’s buffers. Applications should use the TW_PENDINGXFERS.Count returned from DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER to determine whether or not there are more images to be transferred.

Source



Values

Type: TW_BOOL






Required By

None


Chapter 10


None

See Also

CAP_AUTOFEEDCAP_CLEARBUFFERSCAP_MAXBATCHBUFFERS

DG_CONTROL / DAT_PENDINGXFERS / MSG_STOPFEEDER


CAP_BATTERYMINUTES

Description

The minutes of battery power remaining to the device.

Source

-2 indicates that the available power is infinite.

-1 indicates that the device cannot report the remaining battery power.

0 and greater indicates the minutes of battery life remaining.



Values

Type: TW_INT32


Allowed Values: -2, -1, 0, and greater


Container for MSG_SET: MSG_SET not allowed


Required By

None


None

See Also

CAP_POWERSUPPLY, CAP_BATTERYPERCENTAGE


Chapter 10

CAP_BATTERYPERCENTAGE

Description

When used with MSG_GET, return the percentage of battery power level on camera. If -1 is returned, it indicates that the battery is not present.

Application

Use this capability with MSG_GET to indicate to the user about the battery power status. It is recommended to use CAP_POWERSUPPLY to identify the power source first.

Source

-2 indicates that the available power is infinite.

-1 indicates that the device cannot report the remaining battery power.

0 to 100 indicates the percentage of battery life remaining.



Values

Type: TW_INT16

Default Value: None

Allowed Values: -2, -1, 0 to 100.


Container for MSG_SET: Not allowed


Required By

None. Highly recommended for digital cameras that are equipped with batteries.


MSG_GET

See Also

CAP_POWERSUPPLY,CAP_BATTERYMINUTES


CAP_CAMERAENABLED

Description

If set to true the device will deliver images from the current camera.

Source

This feature depends on “camera addressing”, the ability to address elements in the device responsible for the various color spaces. To reduce ambiguity the driver must support either DAT_FILESYSTEM or CAP_CAMERASIDE, and must specifically address the desired camera, even if the device is simplex.

If CAP_CAMERASIDE is supported, the application can use it to set the driver up for bottom (rear) only scanning. Set CAP_CAMERASIDE to TWCS_BOTTOM and set CAP_CAMERAENABLED to TRUE, then set CAP_CAMERASIDE to TWCS_TOP and set CAP_CAMERAENABLED to FALSE.

If DAT_FILESYSTEM is supported, then the application may be able to enter Single Document Multiple Images (SDMI) mode. In this mode the application can independently address the color, grayscale, bitonal, top and bottom cameras as supported by the driver. If the application sets CAP_CAMERAENABLEED to TRUE for more than one “pixel type” on the same camera side, (for instance, color and bitonal on the front) then the driver will output multiple images for that side of the document.


Note: It is not recommended that applications mix the use of ICAP_PIXELTYPE with DAT_FILESYSTEM or CAP_CAMERASIDE. ICAP_PIXELTYPE is intended for simple applications that only want to choose color, grayscale or bitonal. Applications that want to provide bottom (rear) only scanning should use DAT_FILESYSTEM or CAP_CAMERASIDE. Applications that want to provide Single Document Multiple Images should use DAT_FILESYSTEM.

Values

Type: TW_BOOL

Default Value: Dependent on ICAP_PIXELTYPE





Required By

None


Chapter 10


MSG_GETMSG_GETCURRENTMSG_GETDEFAULTMSG_RESETMSG_SET

See Also

CAP_CAMERASIDECAP_CAMERAORDER



CAP_CAMERAORDER

Description

This capability selects the order of output for Single Document Multiple Image mode based on an array of pixel types. For example, if the scanner is set up to deliver color and bitonal documents on the top (front) camera, then an array of {TWPT_RGB, TWPT_BW} will deliver first the color image, then the bitonal image, while an array of {TWPT_BW, TWPT_RGB} will deliver firs the bitonal image, then the color image.

Source

Camera ordering only applies if CAP_CAMERAENABLED is set for more than one pixel type on the same camera, putting the scanner into Single Document Multiple Images mode. DAT_FILESYSTEM is required to perform the proper addressing.

The setting applies to both the top (front) and the bottom (rear), it is not allowed to have one ordering for the top and another for the bottom.


Values

Type: TW_UINT16

Default Value: Scanner specific

Allowed Values: All applicable ICAP_PIXELTYPE values




Required By

None



See Also

CAP_CAMERAENABLED



Chapter 10

CAP_CAMERAPREVIEWUI

Description

This capability queries the Source for UI support for preview mode. If TRUE, the Source supports preview UI.

Application

Use this capability to query the preview UI support by the Source. However, the application can choose to use the Source’s UI or not even if the Source supports it.

Source



Values

Type: TW_BOOL

Default Value: None



Container for MSG_SET: Not allowed.


Required By

None. Highly recommended for digital cameras.


MSG_GET


CAP_CAMERASIDE

Description

Provides a simpler way to independently address the top and bottom cameras in a scanning device without going through DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY.

Application

The application changes which camera it is addressing any capability that allows independent values for the top and bottom. Please note that “top” refers to the camera that captures the top of the sheet of paper (sometimes referred to as the “front”).

There is no easy way to determine if a capability supports independent values for the top and bottom, though as a general rule the ICAP_ capabilities are more likely to allow this. An application can determine support by setting one side, then testing the other side to see if it has changed.

The value of CAP_DUPLEXENABLED does not impact the ability of the application to negotiate the top and bottom values. That is, if CAP_DUPLEXENABLED is FALSE CAP_CAMERASIDE can still be set to TWCS_BOTTOM (if CAP_DUPLEX is TRUE).

Source

If set to TWCS_BOTH (the default) then DAT_CAPABILITY / MSG_SET and MSG_RESET operations apply to the top and bottom. MSG_GET operations get their data from the top camera.

If set to TWCS_TOP or TWCS_BOTTOM, and if the capability being negotiated allows separate values for the top and bottom, then only the side addressed by this capability will be changed as part of a MSG_SET or MSG_RESET, or returned as part of a MSG_GET.

If a capability does not allow separate values for the top and bottom (for instance CAP_DUPLEXENABLED), then the current value of CAP_CAMERASIDE has no impact on how it is negotiated.

If DAT_FILESYSTEM is also supported by the source, it must keep it in sync with the current value of this capability.

Consider the following sequence:

CAP_CAMERASIDE set to TWCS_TOPICAP_XRESOLUTION set to 200CAP_CAMERASIDE set to TWCS_BOTTOMICAP_XRESOLUTION set to 300CAP_CAMERASIDE set to TWCS_BOTH

At this point getting the value of ICAP_XRESOLUTION will return a value of 200, even though the bottom is currently set to 300. This is acceptable behavior. It is up to the application to correctly use CAP_CAMERASIDE.


Chapter 10

Values

Type: TW_UINT16

Default Value: TWCS_BOTH

Allowed Values: TWCS_BOTH

TWCS_TOP

TWCS_BOTTOM

Container for MSG_GET: TW_ENUMERATION

TW_ONEVALUE

Container for MSG_SET: TW_ENUMERATION

TW_ONEVALUE


Required By

None


None

See Also



CAP_CAPTION

Description

A general note about the acquired image.

Source

If not supported, the Source should return TWRC_FAILURE / TWCC_CAPUNSUPPORTED.

Values

Type: TW_STR255

Default Value: “\0”





Required By

None


None

See Also

CAP_AUTHORCAP_TIMEDATE


Chapter 10

CAP_CLEARBUFFERS

Description

MSG_GET reports the presence of data in the scanner’s buffers. MSG_SET with a value of TWCB_CLEAR immediately clears the buffers.

Source

MSG_SET: TWCB_AUTO causes the Source to automatically clear the buffers when it transitions from state 4 to state 5, or from state 5 to state 4.

MSG_SET: TWCB_CLEAR causes the Source to immediately clear its buffers.

MSG_SET: TWCB_NOCLEAR causes the Source to preserve images in the buffers. If the Source transitions from state 4 to state 5 with images in its buffer, it will immediately report MSG_XFERREADY, and deliver those images before any new images scanned by the user.



Values

Type: TW_UINT16

Default Value: TWCB_AUTO

Allowed Values: TWCB_AUTOTWCB_CLEARTWCB_NOCLEAR




Required By

None


None

See Also

CAP_AUTOSCANCAP_MAXBATCHBUFFERS


CAP_CLEARPAGE

Description

If TRUE, the Source will eject the current page being acquired from and will leave the feeder acquire area empty.

If CAP_AUTOFEED is TRUE, a fresh page will be advanced.

CAP_FEEDERENABLED must equal TRUE to use this capability.

This capability must have been negotiated as an extended capability to be used in States 5 and 6.

Application

Do a MSG_SET on this capability to advance the document in the feeder acquire area to the output area and abort all transfers pending on this page.

This capability is used in States 5 and 6 by applications controlling the Source’s feeder (usually without the Source user interface).

This capability can also be used while CAP_AUTOFEED equals TRUE to abort all remaining transfers on this page and continue with the next page.

Source


If supported, advance the document in the feeder-acquire area to the output area and abort all pending transfers from this page.

The Source will perform this action once whenever the capability is MSG_SET to TRUE. The Source should then revert the Current value to FALSE.

Values

Type: TW_BOOL






Required By

None


Chapter 10


None

See Also

CAP_AUTOFEEDCAP_EXTENDEDCAPSCAP_FEEDERENABLEDCAP_FEEDERLOADEDCAP_FEEDPAGECAP_REWINDPAGE


CAP_CUSTOMDSDATA

Description

Allows the application to query the data source to see if it supports the new operation triplets DG_CONTROL/ DAT_CUSTOMDSDATA / MSG_GET and DG_CONTROL/ DAT_CUSTOMDSDATA / MSG_SET.

If TRUE, the source will support the DG_CONTROL/ DAT_CUSTOMDSDATA/MSG_GET message.

Source

If not supported, return TWRC_FAILURE/ TWCC_CAPUNSUPPORTED.

Values

Type: TW_BOOL




Container for MSG_SET: Set not allowed


Required By

None


None

See Also

DG_CONTROL/DAT_CUSTOMDSDATA /MSG_GET


Chapter 10

CAP_CUSTOMINTERFACEGUID

Description

Uniquely identifies an interface for a Data Source, so that an Application can properly interpret its custom content.

Application

Use the value from this capability to interpret all of the numeric values referenced in the See Also section below.

Consider the following example, which results in three GUID’s, one for Vendor ABC and two for Vendor XYZ:

• Vendor ABC’s Scanner models Fred and Wilma have a custom capability called CAP_MYFEATURE with a numeric value of 0x8001.

• Vendor XYZ’s Scanner model Barney has a custom capability CAP_OURFEATURE with a numeric value of 0x8001, but their Scanner Model Betty has a different custom capability CAP_BETTERFEATURE with a numeric value of 0x8001.

The challenge for the Application is to know what 0x8001 means. Historically, this has been determined from the Source’s TW_IDENTITY structure. But this is hard to maintain, and requires the Application to constantly update its recognition code, even in the case of Vendor ABC whose interface stays the same from one model to the next.

Using CAP_CUSTOMINTERFACEGUID the Application can immediately identity Vendor ABC’s unique interface, without having to check its TW_IDENTITY structure.

Source

The Source writer is responsible for creating a GUID. This GUID guarantees that the custom numeric values have exactly the same meaning for any Source that reports that GUID.

If you need to create a GUID, but don’t know how, go to the TWAIN Working Group website and click on FAQ.

Values

Type: TW_STR255

Default Value: Same as the current value

Allowed Values: A string in GUID format

{XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX}



Required By

None



MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, MSG_QUERYSUPPORT

See Also

TWDE_CUSTOMEVENTS, DAT_CUSTOMBASE, MSG_CUSTOMBASE, CAP_CUSTOMBASE, TWRC_CUSTOMBASE, TWCC_CUSTOMBASE


Chapter 10

CAP_DEVICEEVENT

Description

MSG_SET selects which events the Application wants the Source to report. MSG_GET gets the current setting. MSG_RESET resets the capability to the empty array (no events set).

TWDE_CHECKAUTOMATICCAPTURE: The automatic capture settings on the device have been changed by the user.

TWDE_CHECKBATTERY: The status of the battery has changed.

TWDE_CHECKFLASH: The flash setting on the device has been changed by the user.

TWDE_CHECKPOWERSUPPLY: The power supply has been changed (for instance, the user may have just connected AC to a device that was running on battery power).

TWDE_CHECKRESOLUTION: The x/y resolution setting on the device has been changed by the user.

TWDE_DEVICEADDED: The user has added a device (for instance a memory card in a digital camera).

TWDE_DEVICEOFFLINE: A device has become unavailable, but has not been removed.

TWDE_DEVICEREADY: The device is ready to capture an image.

TWDE_DEVICEREMOVED: The user has removed a device.

TWDE_IMAGECAPTURED: The user has captured an image to the device’s internal storage.

TWDE_IMAGEDELETED: The user has removed an image from the device’s internal storage.

TWDE_PAPERDOUBLEFEED: Two or more sheets of paper have been fed together.

TWDE_PAPERJAM: The device’s document feeder has jammed.

TWDE_LAMPFAILURE: The device’s light source has failed.

TWDE_CHECKDEVICEONLINE: The device has been turned off and on.

TWDE_POWERSAVE: The device has powered down to save energy.

TWDE_POWERSAVENOTIFY: The device is about to power down to save energy.

TWDE_CUSTOMEVENTS: Baseline for events specific to a given Source.

Application

Set all values and process the TWRC_CHECKSTATUS (if returned) to identify those items supported by the Source.


Source

The startup default must be an empty array. Generate TWRC_CHECKSTATUS and remove unsupported events when an Application requests events not supported by the Source.



Please note that the actions of an Application must never directly generate a device event. For instance, if the user deletes an image using the controls on the device, then the Source should generate an event. If, however, an Application deletes an image in the device (using DG_CONTROL / DAT_FILESYSTEM / MSG_DELETE), then the Source must not generate an event.

Values

Type: TW_UINT16

Default Value: (empty array)

Allowed Values: TWDE_CHECKAUTOMATICCAPTURETWDE_CHECKBATTERYTWDE_CHECKDEVICEONLINETWDE_CHECKFLASHTWDE_CHECKPOWERSUPPLYTWDE_CHECKRESOLUTIONTWDE_DEVICEADDEDTWDE_DEVICEOFFLINETWDE_DEVICEREADYTWDE_DEVICEREMOVEDTWDE_IMAGECAPTUREDTWDE_IMAGEDELETEDTWDE_PAPERDOUBLEFEEDTWDE_PAPERJAMTWDE_LAMPFAILURETWDE_POWERSAVETWDE_POWERSAVENOTIFYTWDE_CUSTOMEVENTS 0x8000




Required By

None


None


Chapter 10

See Also

DG_CONTROL / DAT_NULL / MSG_DEVICEEVENTDG_CONTROL / DAT_DEVICEEVENT / MSG_GET

Device Events Article


CAP_DEVICEONLINE

Description

If TRUE, the physical hardware (e.g., scanner, digital camera, image database, etc.) that represents the image source is attached, powered on, and communicating.

Application

This capability can be issued at any time to determine the availability of the image source hardware.

Source

The receipt of this capability request should trigger a test of the status of the physical link to the image source. The source should not assume that the link is still active since the last transaction, but should issue a transaction that actively tests this condition.

Values

Type: TW_BOOL

Default Value: None





Required By

All image Sources


MSG_GET/CURRENT/DEFAULT


Chapter 10

CAP_DEVICETIMEDATE

Description

The date and time of the device’s clock.

Managed in the form “YYYY/MM/DD HH:mm:SS:sss” where YYYY is the year, MM is the numerical month, DD is the numerical day, HH is the hour, mm is the minute, SS is the second, and sss is the millisecond.

Source

The internal date and time of the device. Be sure to leave the space between the ending of the date and the beginning of the time fields. All fields must be specified for MSG_SET.



Values

Type: TW_STR32


Allowed Values: Any date




Required By

None


None

See Also

ICAP_TIMEDATE


CAP_DUPLEX

Description

This indicates whether the scanner supports duplex. If so, it further indicates whether one-path or two-path duplex is supported.

Application

Application can send MSG_GET to find out whether the scanner supports duplex.

Source

Source should determine level of duplex support returning the values accordingly.

Values

Type: TW_UINT16

Default Value: TWDX_NONE

Allowed Values: TWDX_NONETWDX_1PASSDUPLEXTWDX_2PASSDUPLEX


Container for MSG_SET: Not allowed.


Required By

None


-

See Also

CAP_DUPLEXENABLED


Chapter 10

CAP_DUPLEXENABLED

Description

The user can set the duplex option to be TRUE or FALSE. If TRUE, the scanner scans both sides of a paper; otherwise, the scanner will scan only one side of the image.

Application

Application should send MSG_GETCURRENT to determine if the duplex option is enabled or not.

Source

Source should return TRUE or FALSE based on the level of duplex support; otherwise, return TWRC_FAILURE / TWCC_CAPUNSUPPORTED.

Values

Type: TW_BOOL






Required By

None


-

See Also

CAP_DUPLEX


CAP_ENABLEDSUIONLY

Description

Allows an application to query a source to see if it implements the new user interface settings dialog. If a source reports that it has the capability CAP_ENABLEDSUIONLY, then it must implement the operation triplet DG_CONTROL/ DAT_USERINTERFACE/ MSG_ENABLEDSUIONLY to display the source user interface without acquiring an image.

If TRUE, the source will support the DG_CONTROL/ DAT_USERINTERFACE /MSG_ENABLEDSUIONLY message.

Source


Values

Type: TW_BOOL




Container for MSG_SET: Set not allowed


Required By

None.


None

See Also

DG_CONTROL/DAT_USERINTERFACE/MSG_ENABLEDSUIONLY


Chapter 10

CAP_ENDORSER

Description

Allows the application to specify the starting endorser / imprinter number. All other endorser/ imprinter properties should be handled through the data source’s user interface.

The user can set the starting number for the endorser.

Source


Values

Type: TW_UINT32

Default Value: 0

Allowed Values: Any value




Required By

None


-

See Also

None


CAP_EXTENDEDCAPS

Description

Allows the application and Source to negotiate capabilities to be used in States 5 and 6.

Application

MSG_GETCURRENT provides a list of all capabilities which the Source and application have agreed to negotiate in States 5 and 6.

MSG_GET provides a list of all capabilities the Source is willing to negotiate in States 5 and 6.

MSG_SET specifies which capabilities the application wants to negotiate in States 5 and 6.

Source


Values

Type: TW_UINT16


Allowed Values: Any xCAP_xxxx




Required By

None


None

See Also

CAP_SUPPORTEDCAPS


Chapter 10

CAP_FEEDERALIGNMENT

Description

Helps the Application determine any special actions it may need to take when negotiating frames with the Source.

TWFA_NONE: The alignment is free-floating. Applications should assume that the origin for frames is on the left.

TWFA_LEFT: The alignment is to the left.

TWFA_CENTER: The alignment is centered. This means that the paper will be fed in the middle of the ICAP_PHYSICALWIDTH of the device. If this is set, then the Application should calculate any frames with a left offset of zero.

TWFA_RIGHT: The alignment is to the right.

Application

The Application can use this to determine if it must center the framing information sent to the Source. With some Sources it might be possible for the Application to select whether the paper is center fed or not.

Source

Use this capability to report the state of the feeder.


Values

Type: TW_UINT16


Allowed Values: TWFA_NONETWFA_LEFTTWFA_CENTERTWFA_RIGHT


Container for MSG_SET: TW_ONEVALUE, if supported


Required By

None


None


CAP_FEEDERENABLED

Description

If TRUE, Source must acquire data from the document feeder acquire area and other feeder capabilities can be used. If FALSE, Source must acquire data from the non-feeder acquire area and no other feeder capabilities can be used.

Application

The application should MSG_SET this capability to TRUE before attempting to use any other feeder capabilities. This sets the current acquire area to the feeder area (it may not be a different physical area on some Sources).

The application can MSG_SET this capability to FALSE to use the Source’s non-feeder acquisition area and disallow the further use of feeder capabilities.

Source

This setting should reflect the current acquire area:

If TRUE, feeder acquire area should be usedIf FALSE, use non-feeder acquire area

Usually, the feeder acquire area and non-feeder acquire area of the Source will be the same. For example, a flatbed scanner may feed a page onto the flatbed platen then scanning always takes place from the platen.

The counter example is a flatbed scanner that moves the scan bar over the platen when CAP_FEEDERENABLED is FALSE, but moves the paper over the scan bar when it is TRUE.

Default Support Guidelines for Sources

• Flatbed scanner (without an optional ADF installed) - Default to FALSE. Do not allow setting to TRUE (return TWRC_FAILURE / TWCC_BADVALUE) but support the capability (never return TWRC_FAILURE / TWCC_CAPUNSUPPORTED).

• A device that uses the same acquire area for feeder and non-feeder, and has a feeder installed - Default to TRUE and allow settings to TRUE or FALSE (meaning allow or don’t allow other feeder capabilities).

• A device that operates differently when acquiring from the feeder and non-feeder areas (for example, physical pages sizes are different) - Default to preferred area and allow setting to either TRUE or FALSE.

• A sheet feed scanner or image database - Default to TRUE (meaning there is only one acquire area - the feeder area) and do not allow setting to FALSE (return TWRC_FAILURE / TWCC_BADVALUE).

• A handheld scanner would not support this capability (return TWRC_FAILURE / TWCC_CAPUNSUPPORTED).


Chapter 10

Values

Type: TW_BOOL






Required By

All Sources with feeder devices



See Also

CAP_AUTOFEEDCAP_CLEARPAGECAP_FEEDERLOADEDCAP_FEEDERPOCKETCAP_FEEDERPREPCAP_FEEDPAGECAP_REWINDPAGE


CAP_FEEDERLOADED

Description

Reflect whether there are documents loaded in the Source’s feeder.

Application

Used by application to inquire whether there are documents loaded in the Source’s feeder.


Source


If CAP_FEEDERENABLED equals TRUE, return the status of the feeder (documents loaded = TRUE; no documents loaded = FALSE).

The Source is responsible for reporting instructions to users on using the device. This includes instructing the user to place documents in the feeder when CAP_FEEDERLOADED equals FALSE and the application has requested a feed page (manually or automatically).

Values

Type: TW_BOOL






Required By

All Sources with feeder devices



See Also

CAP_AUTOFEEDCAP_CLEARPAGECAP_FEEDERENABLEDCAP_FEEDPAGECAP_REWINDPAGE


Chapter 10

CAP_FEEDERORDER

Description

TWFO_FIRSTPAGEFIRST if the feeder starts with the top of the first page. TWFO_LASTPAGEFIRST is the feeder starts with the top of the last page.

Application

An Application can use this to determine if it should reorganize the stream of images received from a Source.



Values

Type: TW_UINT16


Allowed Values: TWFO_FIRSTPAGEFIRSTTWFO_LASTPAGEFIRST


Container for MSG_SET: TW_ONEVALUE, if supported


Required By

None


None

See Also

CAP_FEEDERENABLED


CAP_FEEDERPOCKET

Description

Report what pockets are available to receive paper as it exits from the device..

Source

This capability enumerates the available output or collation pockets on the device. TWFP_POCKET1 - TWFP_POCKET16 are organized from top to bottom and left to right, facing in the direction of the motion of the paper.


Values

Type: TW_UINT16

Allowed Values: TWFP_POCKET1 - TWFP_POCKET16TWFP_POCKETERROR




Required By

None


MSG_GET

See Also

CAP_FEEDERENABLEDCAP_MICRENABLED


Chapter 10

CAP_FEEDERPREP

Description

Improve the movement of paper through a scanner ADF.

Source

If CAP_FEEDERENABLED is TRUE, and CAP_FEEDERPREP is TRUE, then the scanner will perform any action needed to improve the movement of paper through the transport.


Values

Type: TW_BOOL



Container for MSG_GET: TW_ONEVALUE,TW_ENUMERATION

Container for MSG_SET: TW_ONEVALUE,TW_ENUMERATION


Required By

None



See Also

CAP_FEEDERENABLEDCAP_MICRENABLED


CAP_FEEDPAGE

Description

If TRUE, the Source will eject the current page and advance the next page in the document feeder into the feeder acquire area.

If CAP_AUTOFEED is TRUE, the same action just described will occur and CAP_AUTOFEED will remain active.



Application

Do a MSG_SET to TRUE on this capability to advance the next document in the feeder to the feeder acquire area.

This capability is used in States 5 and 6 by applications controlling the Source’s feeder (usually without the Source’s user interface).

This capability can also be used while CAP_AUTOFEED equals TRUE to abort all remaining transfers on this page and continue with the next page.

Source


If supported, advance the document in the feeder-acquire area to the output area and abort all pending transfers from this page.

Advance the next page in the input area to the feeder acquire area. If there are no documents in the input area, return: TWRC_FAILURE / TWCC_BADVALUE.


Values

Type: TW_BOOL







Chapter 10

Required By

None


None

See Also

CAP_AUTOFEEDCAP_CLEARPAGECAP_EXTENDEDCAPSCAP_FEEDERENABLEDCAP_FEEDERLOADEDCAP_REWINDPAGE


CAP_INDICATORS

Description

If TRUE, the Source displays a progress indicator during acquisition and transfer, regardless of whether the Source's user interface is active. If FALSE, the progress indicator is suppressed if the Source's user interface is inactive.

The Source displays device-specific instructions and error messages if either the user interface or progress indicator is turned on. In this case it returns TWCC_OPERATIONERROR to alert the application that it handled the error, and communicated the problem to the user.

If both the user interface and progress indicator are turned off, then the Source never displays any message to the user, even if TWCC_OPERATIONERROR is returned. Messages to the user are under the sole control of the Application.

Application

If the application plans to enable the Source with TW_USERINTERFACE. ShowUI = FALSE, it can also suppress the Source’s progress indicator by using this capability.

Source


Values

Type: TW_BOOL

Default Value: TRUE





Required By

None


None

See Also



Chapter 10

CAP_JOBCONTROL

Description

Allows multiple jobs in batch mode. The application can decide how the job can be processed, according to the flags listed below.

TWJC_NONE No job control.

TWJC_JSIC Detect and include job separator and continue scanning.

TWJC_JSIS Detect and include job separator and stop scanning.

TWJC_JSXC Detect and exclude job separator and continue scanning.

TWJC_JSXS Detect and exclude job separator and stop scanning.

If application selects options other than none, it should check the JCL field of the new PENDINGXFERS data.

To distinguish between jobs, a job separator sheet containing patch code can be inserted. If the application knows the how to save different jobs, the TWJC_JSIC or TWJC_JSXC can be used. When this job separator is detected, the application will give a separate name for each job. If the application does not know how to save different jobs, it can use TWJC_JSIS or TWJC_JSXS to stop scanning and ask the user for different job name.

Source


Values

Type: TW_UINT16

Default Value: TWJC_NONE

Allowed Values: TWJC_NONETWJC_JSICTWJC_JSISTWJC_JSXCTWJC_JSXS

Container for MSG_GET: TW_ONEVALUE/TW_ENUMERATION



Required By

None


None


See Also

MSG_PENDINGXFER


Chapter 10

CAP_LANGUAGE

Description

Allows Application and Source to identify which languages they have in common for the exchange of string data, and to select the language of the internal UI.

Note: Since the TWLG_xxxx codes include language and country data, there is no separate capability for selecting the country.

Application

In multi-lingual environments, it is the responsibility of the Application to recall the last selected language for a given User.

Source

The current value of this setting specifies the language used by the Source (and possibly the device). The Source must first default to the Application’s current language. If that fails then it must default to the User’s Locale (c.f., the Win32 call GetLocaleInfo()). If that fails then the Source should make the best choice it can, preferably using a common secondary language (i.e., English, French…).



Note:

• TWLG_ARABIC_UAE is for the United Arabic Emirates.

• TWLG_CHINESE_PRC is for the People’s Republic of China

Values

Type: TW_UINT16

Default Value: In order of priority:1) appIdentity->Version.Language2) TWLG_USERLOCALE3) Source’s choice

Allowed Values: TWLG_USERLOCALE// pre 1.8 values…

TWLG_DANTWLG_DUTTWLG_ENGTWLG_FCFTWLG_FINTWLG_FRN


TWLG_GERTWLG_ICETWLG_ITNTWLG_NORTWLG_PORTWLG_SPATWLG_SWETWLG_USA// 1.8 should use these…TWLG_AFRIKAANSTWLG_ALBANIATWLG_ARABICTWLG_ARABIC_ALGERIATWLG_ARABIC_BAHRAINTWLG_ARABIC_EGYPTTWLG_ARABIC_IRAQTWLG_ARABIC_JORDANTWLG_ARABIC_KUWAITTWLG_ARABIC_LEBANONTWLG_ARABIC_LIBYATWLG_ARABIC_MOROCCOTWLG_ARABIC_OMANTWLG_ARABIC_QATARTWLG_ARABIC_SAUDIARABIATWLG_ARABIC_SYRIATWLG_ARABIC_TUNISIATWLG_ARABIC_UAETWLG_ARABIC_YEMENTWLG_BASQUETWLG_BYELORUSSIANTWLG_BULGARIANTWLG_CATALANTWLG_CHINESETWLG_CHINESE_HONGKONGTWLG_CHINESE_PRCTWLG_CHINESE_SINGAPORETWLG_CHINESE_SIMPLIFIEDTWLG_CHINESE_TAIWANTWLG_CHINESE_TRADITIONALTWLG_CROATIATWLG_CZECHTWLG_DANISHTWLG_DUTCHTWLG_DUTCH_BELGIANTWLG_ENGLISHTWLG_ENGLISH_AUSTRALIANTWLG_ENGLISH_CANADIANTWLG_ENGLISH_IRELANDTWLG_ENGLISH_NEWZEALANDTWLG_ENGLISH_SOUTHAFRICATWLG_ENGLISH_UKTWLG_ENGLISHTWLG_ESTONIANTWLG_FAEROESE


Chapter 10

TWLG_FARSITWLG_FINNISHTWLG_FRENCHTWLG_FRENCH_BELGIANTWLG_FRENCH_CANADIANTWLG_FRENCH_LUXEMBOURGTWLG_FRENCH_SWISSTWLG_GERMANTWLG_GERMAN_AUSTRIANTWLG_GERMAN_LUXEMBOURGTWLG_GERMAN_LIECHTENSTEINTWLG_GERMAN_SWISSTWLG_GREEKTWLG_HEBREWTWLG_HUNGARIANTWLG_ICELANDICTWLG_INDONESIANTWLG_ITALIANTWLG_ITALIAN_SWISSTWLG_JAPANESETWLG_KOREANTWLG_KOREAN_JOHABTWLG_LATVIANTWLG_LITHUANIANTWLG_NORWEGIANTWLG_NORWEGIAN_BOKMALTWLG_NORWEGIAN_NYNORSKTWLG_POLISHTWLG_PORTUGUESETWLG_PORTUGUESE_BRAZILTWLG_ROMANIANTWLG_RUSSIANTWLG_SERBIAN_LATINTWLG_SLOVAKTWLG_SLOVENIANTWLG_SPANISHTWLG_SPANISH_MEXICANTWLG_SPANISH_MODERTWLG_SWEDISHTWLG_THAITWLG_TURKISHTWLG_UKRANIANTWLG_ASSAMESETWLG_BENGALITWLG_BIHARITWLG_BODOTWLG_DOGRITWLG_GUJARATITWLG_HARYANVITWLG_HINDITWLG_KANNADATWLG_KASHMIRITWLG_MALAYALAMTWLG_MARATHI


TWLG_MARWARITWLG_MEGHALAYANTWLG_MIZOTWLG_NAGATWLG_ORISSITWLG_PUNJABITWLG_PUSHTUTWLG_SERBIAN_CYRILLICTWLG_SIKKIMITWLG_SWEDISH_FINLANDTWLG_TAMILTWLG_TELUGUTWLG_TRIPURITWLG_URDUTWLG_VIETNAMESE

Container for MSG_GET: TW_ENUMERATION, TW_ONEVALUE

Container for MSG_SET: TW_ENUMERATION, TW_ONEVALUE


Required By

None


None


Chapter 10

CAP_MAXBATCHBUFFERS

Description

Describes the number of pages that the scanner can buffer when CAP_AUTOSCAN is enabled.

Application

MSG_GET returns the supported values

MSG_SET sets the current number pages to be buffered (if the Source allows this to be set)

Source

If supported, report the maximum batch buffer settings during MSG_GET. If MSG_SET is supported, limit batch buffers to the requested value for future transfers.


If Operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CONTROL / DAT_CAPABILITY / MSG_QUERYSUPPORT)

Values

Type: TW_UINT32


Allowed Values: 1 to 232 –1

Container for MSG_GET: TW_ONEVALUETW_ENUMERATIONTW_RANGE



Required By

None


None

See Also

CAP_AUTOSCANCAP_CLEARBUFFERS


CAP_MICRENABLED

Description

Get this capability to determine if the Source supports check scanning. If set to TRUE check scanning is enabled, if set to FALSE check scanning is disabled.

Source

When disabled the scanner ignores all related capabilities (refer to the See Also section).


Values

Type: TW_BOOL



Container for MSG_GET: TW_ONEVALUE,TW_ENUMERATION

Container for MSG_SET: TW_ONEVALUE,TW_ENUMERATION


Required By

None



See Also

CAP_FEEDERPREPCAP_FEEDERPOCKET

DG_CONTROL / DAT_EXTIMAGEINFO / MSG_GET


Chapter 10

CAP_PAPERDETECTABLE

Description

This capability determines whether the device has a paper sensor that can detect documents on the ADF or Flatbed.

Application

If the source returns FALSE, the application should not rely on values such as CAP_FEEDERLOADED, and continue as if the paper is loaded.

Source

If supported, the source is responsible for detecting whether document is loaded or not.


If Operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CONTROL/DAT_CAPABILITY/MSG_QUERYSUPPORT)

Values

Type: TW_BOOL

Default Value: TRUE





Required By

None


None

See Also

CAP_FEEDERLOADED


CAP_POWERSAVETIME

Description

When used with MSG_SET, set the camera power down timer in seconds. When used with MSG_GET, return the current setting of the power down time.

Application

Use this capability with MSG_SET to set the user selected camera power down time, when no activity is detected by the camera. The default value of -1 means no power down, power is always on.

Source



Values

Type: TW_INT32

Default Value: -1

Allowed Values: >= -1




Required By

None. Highly recommended for digital cameras. MSG_GET, MSG_SET, MSG_RESET


-

See Also

-


Chapter 10

CAP_POWERSUPPLY

Description

MSG_GET reports the kinds of power available to the device. MSG_GETCURRENT reports the current power supply in use.

Source



Values

Type: TW_UINT16


Allowed Values: TWPS_EXTERNALTWPS_BATTERY

Container for MSG_GET: TW_ENUMERATION,TW_ONEVALUE



Required By

None


None


CAP_PRINTER

Description

MSG_GET returns the current list of available printer devices, along with the one currently being used for negotiation. MSG_SET selects the current device for negotiation, and optionally constrains the list. MSG_RESET restores all the available devices (useful after MSG_SET has been used to constrain the list).

Top/Bottom refer to duplex devices, and indicate if the printer is writing on the top or the bottom of the sheet of paper. Simplex devices use the top settings.

Before/After indicates whether printing occurs before or after the sheet of paper has been scanned.

Application

Use this capability to determine which printers are available for negotiation, and to select a specific printer prior to negotiation.

Source

Imprinters are used to print data on documents at the time of scanning, and may be used for any purpose. Endorsers are more specific in nature, stamping some kind of proof of scanning on the document. Applications may opt to use imprinters for endorsing documents.



Values

Type: TW_UINT16


Allowed Values: TWPR_IMPRINTERTOPBEFORETWPR_IMPRINTERTOPAFTERTWPR_IMPRINTERBOTTOMBEFORETWPR_IMPRINTERBOTTOMAFTERTWPR_ENDORSERTOPBEFORETWPR_ENDORSERTOPAFTERTWPR_ENDORSERBOTTOMBEFORETWPR_ENDORSERBOTTOMAFTER


Container for MSG_SET: TW_ENUMERATION,TW_ONEVALUE



Chapter 10

Required By

None


None

See Also

CAP_PRINTERENABLEDCAP_PRINTERINDEXCAP_PRINTERMODECAP_PRINTERSTRINGCAP_PRINTERSUFFIX


CAP_PRINTERENABLED

Description

Turns the current CAP_PRINTER device on or off.

Source



Values

Type: TW_BOOL






Required By

None


None

See Also

CAP_PRINTERCAP_PRINTERINDEXCAP_PRINTERMODECAP_PRINTERSTRINGCAP_PRINTERSUFFIX


Chapter 10

CAP_PRINTERINDEX

Description

The User can set the starting number for the current CAP_PRINTER device.

Source

This value allows the user to set the starting page number for the current CAP_PRINTER device.



Values

Type: TW_UINT32

Default Value: 0

Allowed Values: Any values.




Required By

None

See Also

CAP_PRINTERCAP_PRINTERENABLEDCAP_PRINTERMODECAP_PRINTERSTRINGCAP_PRINTERSUFFIX


CAP_PRINTERMODE

Description

Specifies the appropriate current CAP_PRINTER device mode.

Note:

• TWPM_SINGLESTRING specifies that the printed text will consist of a single string.

• TWPM _MULTISTRING specifies that the printed text will consist of an enumerated list of strings to be printed in order.

• TWPM _COMPOUNDSTRING specifies that the printed string will consist of a compound of a String followed by a value followed by a suffix string.

Application

Negotiate this capability to specify the mode of printing to use when the current CAP_PRINTER device is enabled.

Source

If supported, use the specified mode for future image acquisitions.



Values

Type: TW_UINT16

Default Value: TWPM_SINGLESTRING

Allowed Values: TWPM_SINGLESTRINGTWPM_MULTISTRINGTWPM_COMPOUNDSTRING




Required By

None


None


Chapter 10

See Also

CAP_PRINTERCAP_PRINTERENABLEDCAP_PRINTERINDEXCAP_PRINTERSTRINGCAP_PRINTERSUFFIX


CAP_PRINTERSTRING

Description

Specifies the string(s) that are to be used in the string component when the current CAP_PRINTER device is enabled.

Application

Negotiate this capability to specify the string or strings to be used for printing (depending on printer mode). Use enumeration to print multiple lines of text, one line per string in the enumerated list. Be sure to check the status codes if attempting multiple lines, since not all devices support this feature.

Source

If supported, use the specified string for printing during future acquisitions.



Values

Type: TW_STR255






Required By

None


None

See Also

CAP_PRINTERCAP_PRINTERENABLEDCAP_PRINTERINDEXCAP_PRINTERMODECAP_PRINTERSUFFIX


Chapter 10

CAP_PRINTERSUFFIX

Description

Specifies the string that shall be used as the current CAP_PRINTER device’s suffix.

Application

Negotiate this capability to specify the string that is used as the suffix for printing if TWPM_COMPOUNDSTRING is used.

Source



Values

Type: TW_STR255






Required By

None


None

See Also

CAP_PRINTERCAP_PRINTERENABLEDCAP_PRINTERINDEXCAP_PRINTERMODECAP_PRINTERSTRING


CAP_REACQUIREALLOWED

Description

Indicates whether the physical hardware (e.g. scanner, digital camera) is capable of acquiring multiple images of the same page without changes to the physical registration of that page.

Application

Use this capability to enable or disable modes of operation where multiple image acquisitions of the page are required. Examples: preview mode, automated image analysis mode.

Source

If supported, return TRUE if the device is capable of capturing the page image multiple times without refeeding the page or otherwise causing physical registration changes. Return FALSE otherwise.



Support Guidelines for Sources

• A flat bed scanner that can retain the page on the platen and moves the scan bar past the page would return TRUE.

• A sheet-fed scanner that physically moves the page past the scan bar would return FALSE.

• A hand held scanner would return FALSE.

Values

Type: TW_BOOL






Required By

None


None


Chapter 10

See Also

CAP_AUTOFEEDCAP_CLEARPAGECAP_FEEDERENABLEDCAP_FEEDPAGECAP_REWINDPAGE


CAP_REWINDPAGE

Description

If TRUE, the Source will return the current page to the input side of the document feeder and feed the last page from the output side of the feeder back into the acquisition area.

If CAP_AUTOFEED is TRUE, automatic feeding will continue after all negotiated frames from this page are acquired.



Application

This capability is used in States 5 and 6 by applications controlling the Source’s feeder (usually without the Source’s user interface).

If CAP_AUTOFEED is TRUE, the normal automatic feeding will continue after all frames of this page are acquired.

Source


If there are no documents in the output area, return: TWRC_FAILURE / TWCC_BADVALUE.


Values

Type: TW_BOOL






Required By

None


Chapter 10


None

See Also

CAP_AUTOFEEDCAP_CLEARPAGECAP_EXTENDEDCAPSCAP_FEEDERENABLEDCAP_FEEDERLOADEDCAP_FEEDPAGE


CAP_SEGMENTED

Description

Describes the segmentation setting for captured images. Image segmentation occurs when either the device or the Source breaks up an image into a stream of image components (text, pictures, graphics) that must be assembled by the application to reconstruct the original document. Applications must use the DAT_EXTIMAGEINFO / TWEI_SEGMENTNUMBER field to identify pieces of an image that are associated with each other through segmentation.

Application

Applications should be able to Get/Set whether segmentation will be applied to captured images.

Source


Values

Type: TW_UINT16

Default Value: TWSG_NONE

Allowed Values: TWSG_AUTO, TWSG_NONE


Container for MSG_SET: TW_ENUMERATION TW_ONEVALUE


Required By

None



See Also

DAT_EXTIMAGEINFO (TWEI_SEGMENTNUMBER)DAT_IMAGELAYOUTTW_IMAGELAYOUT


Chapter 10

CAP_SERIALNUMBER

Description

A string containing the serial number of the currently selected device in the Source. Multiple devices may all report the same serial number.

Application

The value is device specific, Applications should not attempt to parse the information.

Source



Values

Type: TW_STR255






Required By

None


None


CAP_SUPPORTEDCAPS

Description

Returns a list of all the capabilities for which the Source will answer inquiries. Does not indicate which capabilities the Source will allow to be set by the application. Some capabilities can only be set if certain setup work has been done so the Source cannot globally answer which capabilities are “set-able.”

Values

Type: TW_UINT16


Allowed Values: Any “get-able” capability




Required By

All Sources



See Also

CAP_EXTENDEDCAPS


Chapter 10

CAP_TIMEBEFOREFIRSTCAPTURE

Description

For automatic capture, this value selects the number of milliseconds before the first picture is to be taken, or the first image is to be scanned.

Source



Values

Type: TW_INT32

Default Value: 0





Required By

None


None

See Also

CAP_AUTOMATICCAPTURECAP_TIMEBETWEENCAPTURESCAP_XFERCOUNT


CAP_TIMEBETWEENCAPTURES

Description

For automatic capture, this value selects the milliseconds to wait between pictures taken, or images scanned.

Source



Values

Type: TW_INT32

Default Value: 0





Required By

None


None

See Also

CAP_AUTOMATICCAPTURECAP_TIMEBEFOREFIRSTCAPTURECAP_XFERCOUNT


Chapter 10

CAP_TIMEDATE

Description

The date and time the image was acquired.

Note: CAP_TIMEDATE does not return the exact time the image was acquired; rather, it returns the closest available approximation of the time the physical phenomena represented by the image was recorded. If the application needs the exact time of acquisition, the application should generate that value itself during the image acquisition procedure.

Stored in the form “YYYY/MM/DD HH:mm:SS.sss” where YYYY is the year, MM is the numerical month, DD is the numerical day, HH is the hour, mm is the minute, SS is the second, and sss is the millisecond.

This capability must be negotiated during State 7 before the call to the DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER triplet. It must also be listed in the CAP_EXTENDEDCAPS capability by the data source.

Source

The time and date when the image was originally acquired (when the Source entered State 7).

Be sure to leave the space between the ending of the date and beginning of the time fields. Pad the unused characters after the string with zeros.


Values

Type: TW_STR32


Allowed Values: Any date




Required By

None


None


See Also

CAP_AUTHORCAP_CAPTION


Chapter 10

CAP_THUMBNAILSENABLED

Description

Allows an application to request the delivery of thumbnail representations for the set of images that are to be delivered.

Setting CAP_THUMBNAILSENABLED to TRUE turns on thumbnail mode. Images transferred thereafter will be sent at thumbnail size (exact thumbnail size is determined by the Data Source). Setting this capability to FALSE turns thumbnail mode off and returns full size images.

Application

A successful set of this capability to TRUE will cause the Source to deliver image thumbnails during normal data transfer operations. This mode remains in effect until this capability is set back to FALSE.

Source

A successful set of this capability to TRUE should enable the delivery of thumbnail images during normal data transfer. Setting this capability to FALSE will disable thumbnail delivery.


Values

Type: TW_BOOL

Default Value: FALSE (do not deliver thumbnails).





Required By

All Image Store Data Sources.


MSG_GET, MSG_SET, MSG_GETCURRENT, MSG_RESET

See Also

ICAP_IMAGEDATASET


CAP_UICONTROLLABLE

Description

If TRUE, indicates that this Source supports acquisition with the UI disabled; i.e., TW_USERINTERFACE’s ShowUI field can be set to FALSE. If FALSE, indicates that this Source can only support acquisition with the UI enabled.

Source

This capability was introduced in TWAIN 1.6. All Sources compliant with TWAIN 1.6 and above must support this capability. Sources that are not TWAIN 1.6-compliant may return TWRC_FAILURE / TWCC_BADCAP if they do not support this capability.

Application

A return value of TWRC_FAILURE / TWCC_CAPUNSUPPORTED indicates that the Source in use is not TWAIN 1.6-compliant. Therefore, the Source may ignore TW_USERINTERFACE’s ShowUI field when MSG_ENABLEDS is issued. See the description of DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS for more details.

Values

Type: TW_BOOL






Required By

All Sources

See Also

CAP_INDICATORSDG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS


Chapter 10

CAP_XFERCOUNT

Description

The application is willing to accept this number of images.

Application

Set this capability to the number of images you are willing to transfer per session. Common values are:

1 Application wishes to transfer only one image this session

-1 Application is willing to transfer multiple images

Source

If the application limits the number of images it is willing to receive, the Source should not make more transfers available than the specified number.

Values

Type: TW_INT16

Default Value: -1

Allowed Values: -1 to 215




Required By

All Sources and applications



See Also

TW_PENDINGXFERS.Count


ICAP_AUTOBRIGHT

Description

TRUE enables and FALSE disables the Source’s Auto-brightness function (if any).

Source

If TRUE, apply auto-brightness function to acquired image before transfer.


Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_BRIGHTNESS


Chapter 10

ICAP_AUTODISCARDBLANKPAGES

Description

Use this capability to have the Source discard blank images. The Application never sees these images during the scanning session.

TWBP_DISABLE – this must be the default state for the Source. It indicates that all images will be delivered to the Application, none of them will be discarded.

TWBP_AUTO – if this is used, then the Source will decide if an image is blank or not and discard as appropriate.

If the specified value is a positive number in the range 0 to 231–1, then this capability will use it as the byte size cutoff point to identify which images are to be discarded. If the size of the image is less than or equal to this value, then it will be discarded. If the size of the image is greater than this value, then it will be kept so that it can be transferred to the Application.

Source



Values

Type: TW_INT32

Default Value: TW_DISABLE

Allowed Values: TWBP_DISABLETWBP_AUTO

Byte count 0 to 231-1




Required By

None


None

See Also

DAT_EXTIMAGEINFO


ICAP_AUTOMATICBORDERDETECTION

Description

Turns automatic border detection on and off.

Application

Negotiate this capability to determine the state of the AutoBorder detection.

ICAP_UNDEFINEDIMAGESIZE must be enabled for this feature to work.

Source

If supported, enable or disable automatic border detection according to the value specified. Default to FALSE for backward compatibility. For this capability to be enabled, ICAP_UNDEFINEDIMAGESIZE must be enabled.



Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_UNDEFINEDIMAGESIZEICAP_AUTOMATICDESKEWICAP_AUTOSIZE


Chapter 10

ICAP_AUTOMATICCROPUSESFRAME

Description

Set TRUE if DAT_IMAGELAYOUT, ICAP_SUPPORTEDSIZES or ICAP_FRAMES reduces the amount of data captured from the device, potentially improving the performance of the driver, even if any automatic detection capability like ICAP_AUTOMATICBORDERDECTION is set TRUE.

Application

If this capability reports TRUE then the Application may assume a performance benefit from specifying a cropping frame using DAT_IMAGELAYOUT, ICAP_SUPPORTEDSIZES or ICAP_FRAMES.

The Application sets the frame after turning on any automated capabilities. For instance, if the Application wants automatic border detection, but knows that the largest paper size it will receive is US Letter, then it sets ICAP_AUTOMATICBORDERDETECTION to TRUE and then sets ICAP_SUPPORTEDSIZES to TWSS_USLETTER.

Source

The Source reports TRUE if it uses the cropping frame specified by DAT_IMAGELAYOUT, ICAP_SUPPORTEDSIZES or ICAP_FRAMES to reduce the amount of data physically transferred from the device to the Source.

The Source is not obligated to exactly match the frame requested by the Application, but it should use it as a hint to improve the performance of the capture.

Values

Type: TW_BOOL

Default Value: (none)


Container for MSG_GET: TW_ONEVALUE, TW_ENUMERATION


Required By

None

Source Operations


See Also

DAT_IMAGELAYOUT, ICAP_AUTOMATICBORDERDETECTION, ICAP_FRAMES, ICAP_SUPPORTEDSIZES


ICAP_AUTOMATICLENGTHDETECTION

Description

Controls the automatic detection of the length of a document, this is intended for use with an Automatic Document Feeder.

Application

If this capability is present, but does not support TWQC_SET when MSG_QUERYSUPPORT is called, then it indicates the fixed behavior of the Source (always TRUE or always FALSE).

If this capability reports TWQC_SET, then the Application can control the automatic detection of the length of a document.

If ICAP_AUTOMATICBORDERDETECTION (which detects width and length) is set to TRUE, then this capability is ignored.

Source

If set to TRUE, the Source automatically crops the height of the image to the length of the document.

If set to FALSE (and assuming ICAP_AUTOMATICBORDERDETECTION is FALSE), the Source returns the full height specified by ICAP_FRAME or DAT_IMAGELAYOUT, regardless of the actual height of the captured document (for instance, a check in an A4 size area).

Values

Type: TW_BOOL




Container for MSG_SET: TW_ONEVALUE, TW_ENUMERATION


Required By

None

Source Operations

MSG_GET, MSG_GETCURRENT, MSG_GETDEFAULT, MSG_RESET, MSG_SET, MSG_QUERYSUPPORT

See Also

DAT_IMAGELAYOUT, ICAP_AUTOMATICBORDERDETECTION, ICAP_FRAMES, ICAP_SUPPORTEDSIZES


Chapter 10

ICAP_AUTOMATICCOLORENABLED

Description

The Source automatically detects the pixel type of the image and returns either a color image or a non-color image specified by ICAP_AUTOMATICCOLORNONCOLORPIXELTYPE.

Application

When the Application sets this capability to TRUE, it must be prepared to receive a mixture of color and non-color images.

Source

When this capability is TRUE the Source automatically determines the pixel type.

Values

Type: TW_BOOL

Default Value: TRUE



Container of MSG_SET: TW_ENUMERATION, TW_ONEVALUE


Required By

None



See Also

ICAP_PIXELTYPE, ICAP_AUTOMATICCOLORNONCOLORPIXELTYPE


ICAP_AUTOMATICCOLORNONCOLORPIXELTYPE

Description

Specifies the non-color pixel type to use when automatic color is enabled.

Application

ICAP_AUTOMATICCOLORENABLED must be TRUE. When it is the Application sets this capability to specify the pixel type the Source uses when transferring non-color images.

Source

When ICAP_AUTOMATICCOLORENABLED is TRUE, this capability determines the pixel type of the non-color images.

Values

Type: TW_UINT16

Default Value: (none)

Allowed Values: TWPT_BW, TWPT_GRAY


Container of MSG_SET: TW_ENUMERATION, TW_ONEVALUE


Required By

None



See Also

ICAP_PIXELTYPE, ICAP_AUTOMATICCOLORENABLED


Chapter 10

ICAP_AUTOMATICDESKEW

Description

Turns automatic deskew correction on and off.

Application

Negotiate this capability to enable or disable Automatic deskew.

Source

If supported, enable or disable the Automatic deskew feature according to the value specified for future transfers. Default to FALSE for backward compatibility. Some Sources may require ICAP_UNDEFINEDIMAGESIZE to be enabled.



Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_AUTOMATICBORDERDETECTIONICAP_AUTOMATICROTATEICAP_AUTOSIZEICAP_UNDEFINEDIMAGESIZE


ICAP_AUTOMATICROTATE

Description

When TRUE this capability depends on intelligent features within the Source to automatically rotate the image to the correct position.

Application

If this capability is set to TRUE, then it must be assumed that no other correction is required (deskew, rotation, etc…); the Source is guaranteeing that it will deliver images in the correct orientation.

Source

There are no criteria for how this automatic rotation is determined. A Source may use a field of text, or some distinguishing non-text field, such as a barcode or a logo, or it may rely on form recognition to help rotate the document.



Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_AUTOMATICDESKEWICAP_ORIENTATIONICAP_ROTATION


Chapter 10

ICAP_AUTOSIZE

Description

Force the output image dimensions to match either the current value of ICAP_SUPPORTEDSIZES or any of its current allowed values.

Source

This capability takes precedence over CAP_AUTOMATICBORDERDETECTION and ICAP_AUTOMATICLENGTHDETECTION.

When this capability is on images will have their dimensions adjusted to exactly match either the current value of ICAP_SUPPORTEDSIZES, if set to TWAS_CURRENT. Or to any of the allowed values in ICAP_SUPPORTEDSIZES, if set to TWAS_AUTO.

If set to TWAS_NONE, then no action is taken.


Values

Type: TW_UINT16

Default Value: TWAS_NONE

Allowed Values: TWAS_NONETWAS_AUTOTWAS_CURRENT


Container for MSG_SET: TW_ENUMERATION


Required By

None



See Also

ICAP_AUTOMATICBORDERDETECTIONICAP_AUTOMATICDESKEWICAP_ORIENTATION


ICAP_ROTATIONICAP_SUPPORTEDSIZES


Chapter 10

ICAP_BARCODEDETECTIONENABLED

Description

Turns bar code detection on and off.

Source

Support this capability if the scanner supports any Bar code recognition. If the device allows this feature to be turned off, then default to off. If the device does not support disabling this feature, report TRUE and disallow attempts to set FALSE.



Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHPRIORITIESICAP_BARCODESEARCHMODEICAP_BARCODEMAXRETRIESICAP_BARCODETIMEOUT


ICAP_BARCODEMAXRETRIES

Description

Restricts the number of times a search will be retried if none are found on each page.

Application

Refine this capability to limit the number of times the bar code search algorithm is retried on a page that contains no bar codes.

Source

If supported, limit the number of retries the value specified.



Values

Type: TW_UINT32



Container for MSG_GET: TW_ENUMERATIONTW_RANGETW_ONEVALUE



Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHPRIORITIESICAP_BARCODESEARCHMODEICAP_BARCODETIMEOUT


Chapter 10

ICAP_BARCODEMAXSEARCHPRIORITIES

Description

The maximum number of supported search priorities.

Application

Query this value to determine how many bar code detection priorities can be set.

Set this value to limit the number of priorities to speed the detection process.

Source

If bar code searches can be prioritized, report the maximum number of priorities allowed for a search.



Values

Type: TW_UINT32






Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODESEARCHPRIORITIESICAP_BARCODESEARCHMODE


ICAP_BARCODEMAXRETRIESICAP_BARCODETIMEOUT


Chapter 10

ICAP_BARCODESEARCHMODE

Description

Restricts bar code searching to certain orientations, or prioritizes one orientation over the other.

Application

Negotiate this capability if the orientation of bar codes is already known to the application. Refinement of this capability can speed the bar code search.

Source

If set then apply the specified refinements to future bar code searches.



Values

Type: TW_UINT16


Allowed Values: TWBD_HORZTWBD_VERTTWBD_HORZVERTTWBD_VERTHORZ




Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHPRIORITIES


ICAP_BARCODEMAXRETRIESICAP_BARCODETIMEOUT


Chapter 10

ICAP_BARCODESEARCHPRIORITIES

Description

A prioritized list of bar code types dictating the order in which bar codes will be sought.

Application

Set this capability to specify the order and priority for bar code searching. Refining the priorities to only the bar code types of interest to the application can speed the search process.

Source

If this type of search refinement is supported, then report the current values.

If set, then limit future searches to the specified bar codes in the specified priority order.


If Operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CONTROL /DAT_CAPABILITY / MSG_QUERYSUPPORT)

Values

Type: TW_UINT16


Allowed Values: TWBT_3OF9TWBT_2OF5INTERLEAVEDTWBT_2OF5NONINTERLEAVEDTWBT_CODE93TWBT_CODE128

TWBT_UCC128TWBT_CODABARTWBT_UPCATWBT_UPCETWBT_EAN8TWBT_EAN13TWBT_POSTNETTWBT_PDF417TWBT_2OF5INDUSTRIALTWBT_2OF5MATRIXTWBT_2OF5DATALOGICTWBT_2OF5IATATWBT_3OF9FULLASCIITWBT_CODABARWITHSTARTSTOPTWBT_MAXICODE

Container for MSG_GET: TW_ ARRAY

Container for MSG_SET: TW_ ARRAY



Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHMODEICAP_BARCODEMAXRETRIESICAP_BARCODETIMEOUT


Chapter 10

ICAP_BARCODETIMEOUT

Description

Restricts the total time spent on searching for a bar code on each page.

Application

Refine this value to tune the length of time the search algorithm is allowed to execute before giving up.

Source

If supported, limit the duration of a bar code search to the value specified.


If Operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CONTROL / DAT_CAPABILITY / MSG_QUERYSUPPORT).

Values

Type: TW_UINT32






Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDBARCODETYPESICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHPRIORITIESICAP_BARCODESEARCHMODEICAP_BARCODEMAXRETRIES


ICAP_BITDEPTH

Description

Specifies the pixel bit depths for the Current value of ICAP_PIXELTYPE. For example, when using ICAP_PIXELTYPE = TWPT_GRAY, this capability specifies whether this is 8-bit gray or 4-bit gray.

This depth applies to all the data channels (for instance, the R, G, and B channels will all have this same bit depth for RGB data).

Application

The application should loop through all the ICAP_PIXELTYPEs it is interested in and negotiate the ICAP_BITDEPTH(s) for each.

For all allowed settings of ICAP_PIXELTYPE

• Set ICAP_PIXELTYPE

• Set ICAP_BITDEPTH for the current ICAP_PIXELTYPE

Source


If the bit depth in a MSG_SET is not supported for the current ICAP_PIXELTYPE setting, return TWRC_FAILURE / TWCC_BADVALUE.

Values

Type: TW_UINT16


Allowed Values: >=1




Required By

All Image Sources




Chapter 10

See Also

ICAP_PIXELTYPE



Description

Specifies the Reduction Method the Source should use to reduce the bit depth of the data. Most commonly used with ICAP_PIXELTYPE = TWPT_BW to reduce gray data to black and white.

Application

Set the capability to the reduction method to be used in future acquisitions

Also select the Halftone or Threshold to be used.

Source


Values

Type: TW_UINT16


Allowed Values: TWBR_THRESHOLDTWBR_HALFTONETWBR_CUSTHALFTONETWBR_DIFFUSION




Required By

None


None

See Also

ICAP_CUSTHALFTONEICAP_HALFTONESICAP_PIXELTYPEICAP_THRESHOLD


Chapter 10

ICAP_BITORDER

Description

Specifies how the bytes in an image are filled by the Source. TWBO_MSBFIRST indicates that the leftmost bit in the byte (usually bit 7) is the byte’s Most Significant Bit.

Source


Values

Type: TW_UINT16

Default Value: TWBO_MSBFIRST

Allowed Values: TWBO_LSBFIRSTTWBO_MSBFIRST




Required By

All Image Sources



See Also

ICAP_BITORDERCODES


ICAP_BITORDERCODES

Description

Used for CCITT data compression only. Indicates the bit order representation of the stored compressed codes.

Source


Values

Type: TW_UINT16

Default Value: TWBO_LSBFIRST

Allowed Values: TWBO_LSBFIRSTTWBO_MSBFIRST




Required By

None


None

See Also

ICAP_COMPRESSION


Chapter 10

ICAP_BRIGHTNESS

Description

The brightness values available within the Source.

Application

The application can use this capability to inquire, set, or restrict the values for BRIGHTNESS used in the Source.

Source

Source should normalize the values into the range. Make sure that a ‘0’ value is available as the Current Value when the Source starts up. If the Source’s ± range is asymmetric about the ‘0’ value, set range maxima to ±1000 and scale homogeneously from the ‘0’ value in each direction. This will yield a positive range whose step size differs from the negative range’s step size.


Values

Type: TW_FIX32

Default Value: 0

Allowed Values: -1000 to +1000

Container for MSG_GET: TW_ENUMERATIONTW_ONEVALUETW_RANGE

Container for MSG_SET: TW_ENUMERATIONTW_ONEVALUETW_RANGE


Required By

None


None

See Also

ICAP_AUTOBRIGHTICAP_CONTRAST


ICAP_CCITTKFACTOR

Description

Used for CCITT Group 3 2-dimensional compression. The ‘K’ factor indicates how often the new compression baseline should be re-established. A value of 2 or 4 is common in facsimile communication. A value of zero in this field will indicate an infinite K factor—the baseline is only calculated at the beginning of the transfer.

Source


Values:

Type: TW_UINT16

Default Value: 4





Required By

None


None

See Also

ICAP_COMPRESSION


Chapter 10

ICAP_COLORMANAGEMENTENABLED

Description

Disables the Source’s color and gamma tables for color and grayscale images, resulting in output that that could be termed “raw”.

Application

When the Application sets this capability to FALSE, it takes responsibility for profiling the color and grayscale output of the device, and applying the desired color and gamma corrections itself. The Application is completely responsible for the quality of the finished image.

Source

When this capability is FALSE the Source turns off as much of its color and gamma correction as it can. There is no universal standard for this behavior, so it makes its best effort.

It is recommended that the Source not expose this capability unless it can do a credible job of outputting “raw” image data.

Values

Type: TW_BOOL

Default Value: TRUE



Container of MSG_SET: TW_ONEVALUE, TW_ENUMERATION


Required By

None



See Also

ICAP_PIXELTYPE


ICAP_COMPRESSION

Description

Allows the application and Source to identify which compression schemes they have in common for Buffered Memory and File transfers.

Note for File transfers:

Since only certain file formats support compression, this capability must be negotiated after setting the desired file format with ICAP_IMAGEFILEFORMAT.

TWCP_NONE All Sources must support this.

TWCP_PACKBITS Macintosh PackBits format, (can be used with TIFF or PICT)

TWCP_GROUP31D,

TWCP_GROUP31DEOL,

TWCP_GROUP32D,

TWCP_GROUP4 Are all from the CCITT specification (now ITU), intended for document images (can be used with TIFF).

TWCP_JPEG Intended for the compression of color photographs (can be used with TIFF, JFIF or SPIFF).

TWCP_LZW A compression licensed by UNISYS (can be used with TIFF).

TWCP_JBIG Intended for bitonal and grayscale document images (can be used with TIFF or SPIFF).

TWCP_PNG This compression can only be used if ICAP_IMAGEFILEFORMAT is set to TWFF_PNG.

TWCP_RLE4,

TWCP_RLE8,

TWCP_BITFIELDS These compressions can only be used if ICAP_IMAGEFILEFORMAT is set to TWFF_BMP.

Application

Applications must not assume that a Source can provide compressed Buffered Memory or File transfers, because many cannot. The application should use MSG_SET on a TW_ONEVALUE container to specify the compression type for future transfers.

Source

The current value of this setting specifies the compression method to be used in future transfers. If the image transfer mechanism is changed, then the allowed list must be modified to reflect the supported values. If the current value is not available on the new allowed list, then the Source must change it to its preferred value.


Chapter 10



Values

Type: TW_UINT16

Default Value: TWCP_NONE

Allowed Values: TWCP_NONETWCP_PACKBITSTWCP_GROUP31DTWCP_GROUP31DEOLTWCP_GROUP32DTWCP_GROUP4TWCP_JPEGTWCP_LZWTWCP_JBIGTWCP_PNGTWCP_RLE4TWCP_RLE8TWCP_BITFIELDS




Required By

All Image Sources



See Also

DG_ CONTROL / DAT_IMAGEMEMFILEXFER / MSG_GETDG_CONTROL / DAT_IMAGEMEMXFER / MSG_GETDG_CONTROL / DAT_IMAGEFILEXFER / MSG_GET

CAP_XFERMECHICAP_IMAGEFILEFORMAT


ICAP_CONTRAST

Description

The contrast values available within the Source.

Application

The application can use this capability to inquire, set or restrict the values for CONTRAST used in the Source.

Source

Scale the values available internally into a homogeneous range between -1000 and 1000. Make sure that a ‘0’ value is available as the Current value when the Source starts up. If the Source’s ± range is asymmetric about the ‘0’ value, set range maxima to ±1000 and scale homogeneously from the ‘0’ value in each direction. This will yield a positive range whose step size differs from the negative range’s step size.


Values

Type: TW_FIX32

Default Value: 0

Allowed Values: -1000 to +1000




Required By

None


None

See Also

ICAP_BRIGHTNESS


Chapter 10

ICAP_CUSTHALFTONE

Description

Specifies the square-cell halftone (dithering) matrix the Source should use to halftone the image.

Application

The application should also set ICAP_BITDEPTHREDUCTION to TWBR_CUSTHALFTONE to use this capability.

Source


Values

Type: TW_UINT8


Allowed Values: Any rectangular array




Required By

None


None

See Also



ICAP_EXPOSURETIME

Description

Specifies the exposure time used to capture the image, in seconds.

Source


Values

Type: TW_FIX32


Allowed Values: >0




Required By

None


None

See Also

ICAP_FLASHUSED2ICAP_LAMPSTATEICAP_LIGHTPATHICAP_LIGHTSOURCE


Chapter 10

ICAP_EXTIMAGEINFO

Description

Allows the application to query the data source to see if it supports the new operation triplet DG_IMAGE/ DAT_EXTIMAGEINFO/ MSG_GET.

If TRUE, the source will support the DG_IMAGE/DAT_EXTIMAGEINFO/MSG_GET message.

Note: The TWAIN API allows for an application to query the results of many advanced device/manufacturer operations. The responsibility of configuring and setting up each advanced operation lies with the device’s data source user interface. Since the configuration of advanced device/manufacturer-specific operations varies from manufacturer to manufacturer, placing the responsibility for setup and configuration of advanced operations allows the application to remain device independent.

Source


Values

Type: TW_BOOL






Required By

None


None

See Also

DG_IMAGE/DAT_EXTIMAGEINFO/MSG_GETICAP_SUPPORTEDEXTIMAGEINFO


ICAP_FEEDERTYPE

Description

Allows the Application to set scan parameters depending upon the type of feeder.

If the Source has a general type of the feeder only, default scan parameters can depend upon the type of scan (general document or photo). In this case, negotiating this capability will allow the Source adjusting the settings accordingly. It is advised, therefore, that this capability be negotiated prior to the capabilities related to specific Source settings (like ICAP_*RESOLUTION, ICAP_PIXELTYPE, etc.) but after the other feeder-related capabilities (CAP_FEEDERENABLED, CAP_FEEDERLOADED).

Application

MSG_GET provides a list of available feeder types.MSG_SET specifies which type of feeder to use.

Source

Use this capability to report either the types of feeders available or (in the case where there is a general type feeder only) the scan types supported through the feeder.


Values

Type: TW_UINT16


Allowed Values: TWFE_GENERAL

TWFE_PHOTO


TW_ONEVALUE



Required By

None


None


Chapter 10

See Also

CAP_FEEDERENABLEDCAP_FEEDERLOADED


ICAP_FILTER

Description

Describes the color characteristic of the subtractive filter applied to the image data. Multiple filters may be applied to a single acquisition.

Source

If the Source only supports application of a single filter during an acquisition and multiple filters are specified by the application, set the current filter to the first one requested and return TWRC_CHECKSTATUS.


Values

Type: TW_UINT16


Allowed Values: TWFT_REDTWFT_GREENTWFT_BLUETWFT_NONETWFT_WHITETWFT_CYANTWFT_MAGENTATWFT_YELLOWTWFT_BLACK

Container for MSG_GET: TW_ARRAYTW_ONEVALUE

Container for MSG_SET: TW_ARRAYTW_ONEVALUE


Required By

None


None


Chapter 10

ICAP_FLASHUSED2

Description

For devices that support flash. MSG_SET selects the flash to be used (if any). MSG_GET reports the current setting. This capability replaces ICAP_FLASHUSED, which is only able to negotiate the flash being on or off.

Application

Note that an image with flash may have a different color composition than an image without flash.

Source



Values

Type: TW_UINT16

Default Value: TWFL_NONE

Allowed Values: TWFL_NONETWFL_OFFTWFL_ONTWFL_AUTOTWFL_REDEYE




Required By

None


None

See Also

ICAP_FLASHUSED


ICAP_FLIPROTATION

Description

Flip rotation is used to properly orient images that flip orientation every other image.

TWFR_BOOK The images to be scanned are viewed in book form, flipping each page from left to right or right to left.

TWFR_FANFOLD The images to be scanned are viewed in fanfold paper style, flipping each page up or down.

On duplex paper, the As are all located on the top, and the Bs are all located on the bottom. If ICAP_FLIPROTATION is set to TWFR_BOOK, and fanfold paper is scanned, then every B image will be upside down. Setting the capability to TWFR_FANFOLD instructs the Source to rotate the B images 180 degrees around the x-axis.

Because this capability is described to act upon every other image, it will work correctly in simplex mode, assuming that every other simplex image is flipped in the manner described above.

Source



Values

Type: TW_UINT16

Default Value: TWFR_BOOK

Allowed Values: TWFR_BOOKTWFR_FANFOLD

Container for MSG_GET: TW_ONEVALUETW_ENUMERATION

Container for MSG_SET: TW_ONEVALUE TW_ENUMERATION


A B BADirection of scan

B

AA

B

Direction of scan


Chapter 10

Required By

None


None


ICAP_FRAMES

Description

The list of frames the Source will acquire on each page.

Application

MSG_GET returns the size and location of all the frames the Source will acquire image data from when acquiring from each page.

MSG_GETCURRENT returns the size and location of the next frame to be acquired.

MSG_SET allows the application to specify the frames and their locations to be used to acquire from future pages.

This ICAP is most useful if the Source supports simultaneous acquisition from multiple frames. Use ICAP_MAXFRAMES to establish this ability.

Source


Values

Type: TW_FRAME


Allowed Values: Device dependent




Required By

None


None

See Also

ICAP_MAXFRAMESICAP_SUPPORTEDSIZESTW_IMAGELAYOUT


Chapter 10

ICAP_GAMMA

Description

Gamma correction value for the image data.

Application

Do not use with TW_CIECOLOR, TW_GRAYRESPONSE, or TW_RGBRESPONSE data.

Source


Values

Type: TW_FIX32

Default Value: 2.2





Required By

None


None


ICAP_HALFTONES

Description

A list of names of the halftone patterns available within the Source.

Application

The application may not rename any halftone pattern.

The application should also set ICAP_BITDEPTHREDUCTION to use this capability.

Values

Type: TW_STR32


Allowed Values: Any halftone name

Container for MSG_GET: TW_ARRAY (for backwards compatibility with 1.0 only)TW_ENUMERATIONTW_ONEVALUE

Container for MSG_SET: TW_ARRAY (for backwards compatibility with 1.0 only)TW_ENUMERATIONTW_ONEVALUE


Required By

None


None

See Also

ICAP_CUSTHALFTONEICAP_BITDEPTHREDUCTIONICAP_THRESHOLD


Chapter 10

ICAP_HIGHLIGHT

Description

Specifies which value in an image should be interpreted as the lightest “highlight.” All values “lighter” than this value will be clipped to this value. Whether lighter values are smaller or larger can be determined by examining the Current value of ICAP_PIXELFLAVOR.

Source

If more or less than 8 bits are used to describe the image, the actual data values should be normalized to fit within the 0-255 range. The normalization need not result in a homogeneous distribution if the original distribution was not homogeneous.


Values

Type: TW_FIX32

Default Value: 255





Required By

None


None

See Also

ICAP_SHADOW


ICAP_ICCPROFILE

Description

Informs the application if the source has an ICC profile and can embed or link it in the current ICAP_IMAGEFILEFORMAT. Tells the source if the application would like an ICC profile embedded or linked into the image file the source will write.

Application

Use this ICAP to determine if the source supports embedding or linking of ICC profiles into files and to control whether or not the source does so.

Source

If not supported, return TWRC_FAILURE/TWCC_CAP_UNSUPPORTED. This should only be supported if ICAP_IMAGEFILEFORMAT is set to a file format that supports the embedding or linking of profiles and the source has an ICC profile it can embed.

Since the given ICAP_PIXELTYPE may not have been determined at the time this is called, the source should ignore the current ICAP_PIXELTYPE. For example, if the source has an ICC profile for color data, but not grayscale or monochrome data, it should offer values as if all pixeltypes are supported.

In the case of TWPT_SRGB, the source should embed the sRGB ICC profile to the file if told to embed a profile.

If operation is not supported, return TWRC_FAILURE, TWCC_CAPBADOPERATION. (See DG_CNTROL / DAT_CAPABILITY / MSG_QUERYSUPORT)

Values

Type: TW_UNIT16

Default Value: TWIC_NONE

Allowed Value: TWIC_NONETWIC_EMBEDTWIC_LINK




Required By

None


None


Chapter 10

See Also

DG_IMAGE/ DAT_ICCPROFILE / MSG_GET


ICAP_IMAGEDATASET

Description

Gets or sets the image indices that will be delivered during the standard image transfer done in States 6 and 7. Indices are assumed to start at 1, so a TW_ONEVALUE container sets an implied range from 1 to the number specified. TW_RANGE returns are useful for those cases where the images are contiguous (5 .. 36). TW_ARRAY returns should be used were index values are discontinuous (as could be the case where the user previously set such a data set). See the note in the Values section below.

Application

A MSG_RESET operation should always be done before a MSG_GET if the application wishes to get the complete list of available images. A MSG_SET operation will define the number and order of images delivered during States 6 and 7.

Source

For MSG_GET, if a contiguous range of images are available starting from the first index (e.g., 1 .. 36) it is recommended that the TW_ONEVALUE container is used specifying just the total number of available images (e.g., 36).


Values

Type: TW_UINT32

Default Value: Entire range or set of available images

Allowed Values: 0 to 232 -1 (for MSG_GET)1 to 232 -1 (for MSG_SET)

Container for MSG_GET: TW_ONEVALUETW_RANGE (see note below)TW_ARRAY (see note below)

Container for MSG_SET: TW_ONEVALUETW_RANGETW_ARRAY


Note: These container types are supported for the returning discontinuous indices that have been previously set by the application. It is highly recommended that for a initialized or reset Image Store device, the TW_ONEVALUE container be the only one returned by the MSG_GET operation. In other words, the data source should not expose the details of the internal memory management of the Image Store device by claiming that it has a hole in its storage locations due to user deletions. For example, a camera that currently has data for pictures 1 to 10 should report that it has 10 images available. If the user later deletes pictures 5, 7, and 9, it should now report that it has 7 images available (i.e., 1 to 7), and not claim that it has pictures 1, 2, 3, 4, 6, 8, and 10 available. To do so would


Chapter 10

expose the internal memory management constraints of the device and serves little use but to confuse the user.

Required By

All Image Store Data Sources.


MSG_GET, MSG_SET, MSG_RESET


ICAP_IMAGEFILEFORMAT

Description

Informs the application which file formats the Source can generate (MSG_GET). Tells the Source which file formats the application can handle (MSG_SET).

TWFF_TIFF Used for document imaging

TWFF_PICT Native Macintosh format

TWFF_BMP Native Microsoft format

TWFF_XBM Used for document imaging

TWFF_JFIF Wrapper for JPEG images

TWFF_FPX FlashPix, used with digital cameras

TWFF_TIFFMULTI Multi-page TIFF files

TWFF_PNG An image format standard intendedfor use on the web, replaces GIF

TWFF_SPIFF A standard from JPEG, intended to replace JFIF, also supports JBIG

TWFF_EXIF File format for use with digital cameras.

TWFF_PDF A file format from Adobe

TWFF_JP2 A file format from the Joint Photographic Experts Group

TWFF_DEJAVU A file format from LizardTech

TWFF_PDFA A file format from Adobe

Application

Use this ICAP to determine which formats are available for file transfers, and set the context for other capability negotiations such as ICAP_COMPRESSION.

Be sure to use the DG_CONTROL / DAT_SETUPFILEXFER / MSG_SET operation to specify the format to be used for a particular acquisition.

Source



Values

Type: TW_UINT16

Default Value: TWFF_BMP (Windows)TWFF_PICT (Macintosh)


Chapter 10

Allowed Values: TWFF_TIFFTWFF_PICTTWFF_BMPTWFF_XBMTWFF_JFIFTWFF_FPXTWFF_TIFFMULTTWFF_PNGTWFF_SPIFFTWFF_EXIFTWFF_PDFTWFF_JP2TWFF_JPXTWFF_DEVAVUTWFF_PDFA




Required By

None


None

See Also

DG_CONTROL / DAT_SETUPFILEXFER / MSG_SETDG_IMAGE / DAT_IMAGEFILEXFER / MSG_GET

ICAP_COMPRESSION


ICAP_IMAGEFILTER

Description

For devices that support image enhancement filtering. This capability selects the algorithm used to improve the quality of the image.

Application

TWIF_LOWPASS is good for halftone images.

TWIF_BANDPASS is good for improving text.

TWIF_HIGHPASS is good for improving fine lines.

Source



Values

Type: TW_UINT16

Default Value: TWIF_NONE

Allowed Values: TWIF_NONETWIF_AUTOTWIF_LOWPASSTWIF_BANDPASSTWIF_HIGHPASSTWIF_TEXTTWIF_FINELINE




Required By

None


None


Chapter 10

ICAP_IMAGEMERGE

Description

Merges the front and rear image of a document in one of four orientations: front on the top, front on the bottom, front on the left or front on the right.

Application

The front and rear have the same settings. It is a customization for a source to allow different settings, for instance a front of TWPT_RGB and a rear of TWPT_BW.

The merged image can be found at an origin of (0, total-image-height / 2) or (total-image-width, 0), depending on the value of this capability.

Use the TWEI_IMAGEMERGED value with DAT_EXTIMAGEINFO to determine if an image is the result of a merge.

Source

This capability only has meaning when scanning duplex.

The source chooses how many differences it wants to support between the front and the rear. The only one it is obligated to deal with is differences in the width and height. In both cases the larger value must be selected, and the extra space in the smaller image filled in with some color.

If the source cannot negotiate this capability because of a difference in the front and rear settings, it returns TWCC_CAPSEQERROR.

Values

Type: TW_UINT16

Default Value: TWIM_NONE

Front or Rear For TWIM_FRONTONTOP and TWIM_FRONTONBOTTOM the final image is twice the pixel height of the larger of the two images. The top image has its origin at the upper left hand corner. The bottom image has its origin on the left but down (total-image-height / 2) pixels.

Rear or Front

Front or Rear

Rear or Front

For TWIM_FRONTONLEFT and TWIM_FRONTONRIGHT the final image is twice the pixel width of the larger of the two images. The left image has its origin at the upper left hand corner. The right image has its origin on the top but left (total-image-width / 2) pixels.


Allowed Values: TWIM_NONE, TWIM_FRONTONTOP, TWIM_FRONTONBOTTOM, TWIM_FRONTONLEFT, TWIM_FRONTONRIGHT




Required By

None

Source Operations


See Also

CAP_DUPLEXENABLED, CAP_IMAGEMERGEHEIGHTTHEASHOLD, TWEI_IMAGEMERGED


Chapter 10

ICAP_IMAGEMERGEHEIGHTTHRESHOLD

Description

Specifies a Y-Offset in ICAP_UNITS units. Front and rear images less than or equal to this value are merged according to the settings of ICAP_IMAGEMERGE. If either the front or the rear image is greater than this value, they are not merged.

Application

The Application specifies this value to help with mixed batches of different paper sizes. For instance, a value of 4.0 inches would be enough to merge check-size documents, while leaving larger paper sizes unmerged.

If ICAP_AUTOMATICDESKEW is FALSE, then this value must allow for image skew in the height. If ICAP_AUTOMATICDESKEW is TRUE, then some small amount above the expected document height is still recommended.

Source

This capability only has meaning when CAP_INDICATORS is set to a value other than TWIM_NONE.

Values

Type: TW_FIX32

Default Value: 0.0

Allowed Values: 0.0 to ICAP_PHYSICALHEIGHT

Container for MSG_GET: TW_ONEVALUE, TW_RANGE



Required By

None

Source Operations


See Also

CAP_INDICATORS


ICAP_JPEGPIXELTYPE

Description

Allows the application and Source to agree upon a common set of color descriptors that are made available by the Source. This ICAP is only useful for JPEG-compressed buffered memory image transfers.

Source


Values

Type: TW_UINT16


Allowed Values: TWPT_BWTWPT_GRAYTWPT_RGBTWPT_PALETTETWPT_CMYTWPT_CMYKTWPT_YUVTWPT_YUVKTWPT_CIEXYZ




Required By

None


None

See Also

ICAP_COMPRESSION


Chapter 10

ICAP_JPEGQUALITY

Description

Use this capability as a shortcut to select JPEG quantization tables that tradeoff quality versus compressed image size. Used in concert with DAT_JPEGCOMPRSSION it is possible for an Application to obtain the tables that are appropriate for varying percentages of quality within a given Source.

TWJQ_UNKNOWN is a read-only value (MSG_GET or MSG_GETCURRENT), the Application cannot set the Source to this value. This value is reported if the Application uses DAT_JPEGCOMPRESSION to select the quantization tables, and the Source is unable to resolve those tables to a percentage value.

The next three TWJQ_ values are intended as markers into the quality range, and are only applicable with MSG_SET.

MSG_GET, MSG_GETCURRENT and MSG_GETDEFAULT only return values in the range 0 – 100. If an Application wishes to map a TWJQ_ value to a corresponding value in the range 0 – 100, then it must issue a MSG_GET after a MSG_SET with one of the three TWJQ_ values.

No assumption is made about the meaning of the range 0 – 99, it may be derived from the JPEG standard or it may be optimized for the Source’s device. 100, though, implies a lossless form of compression. Applications are not encouraged to use this value since it results in poor compression, as well as a format that is not currently widely supported in the industry.

TWJQ_UNKNOWN – read-only; must be the setting for this capability if the user sets the JPEG compression tables using DAT_JPEGCOMPRESSION, and the Source is not able to map the selected tables to a specific percentage of quality.

TWJQ_LOW – write-only; implies low quality; the images are at the maximum compression recommended by the Source.

TWJQ_MEDIUM – write-only; implies medium quality; the images are at the balance point between good compression and good images. This is an arbitrary setting on the part of the Source writer that is expected to best represent their device. This is the value that Applications are most encouraged to use.

TWJQ_HIGH – write-only; implies high quality; the images display the maximum quality that produces any kind of meaningful compression. Note that images at this setting are still considered to be lossy.

Source



Values

Type: TW_INT16



Allowed Values: TWJQ_UNKNOWNTWJQ_LOWTWJQ_MEDIUMTWJQ_HIGH0 - 100

Container for MSG_GET: TW_ENUMERATION,TW_ONEVALUE,TW_RANGE

Container for MSG_SET: TW_ENUMERATION,TW_ONEVALUE,TW_RANGE


Required By

None


None

See Also

DAT_JPEGCOMPRESSION


Chapter 10

ICAP_LAMPSTATE

Description

TRUE means the lamp is currently, or should be set to ON. Sources may not support MSG_SET operations.

Source


Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_EXPOSURETIMEICAP_FLASHUSED2ICAP_LIGHTPATHICAP_LIGHTSOURCE


ICAP_LIGHTPATH

Description

Describes whether the image was captured transmissively or reflectively.

Source


Values

Type: TW_UINT16


Allowed Values: TWLP_REFLECTIVETWLP_TRANSMISSIVE




Required By

None


None

See Also

ICAP_EXPOSURETIMEICAP_FLASHUSED2ICAP_LAMPSTATEICAP_LIGHTSOURCE


Chapter 10

ICAP_LIGHTSOURCE

Description

Describes the general color characteristic of the light source used to acquire the image.

Source


Values

Type: TW_UINT16


Allowed Values: TWLS_REDTWLS_GREENTWLS_BLUETWLS_NONETWLS_WHITETWLS_UVTWLS_IR




Required By

None


None

See Also

ICAP_EXPOSURETIMEICAP_FLASHUSED2ICAP_LAMPSTATEICAP_LIGHTPATH


ICAP_MAXFRAMES

Description

The maximum number of frames the Source can provide or the application can accept per page.

This is a bounding capability only. It does not establish current or future behavior.

Source


Values

Type: TW_UINT16






Required By

None


None

See Also

ICAP_FRAMESTW_IMAGELAYOUT


Chapter 10

ICAP_MINIMUMHEIGHT

Description

Allows the source to define the minimum height (Y-axis) that the source can acquire.

Application

Source

The minimum height that the device can scan. This may be different depending on the value of CAP_FEEDERENABLED.

Values

Type: TW_FIX32


Allowed Values: 0 to 32767 in ICAP_UNITS




Required By

None


See Also

CAP_FEEDERENABLEDICAP_PHYSICALHEIGHTICAP_UNITS


ICAP_MINIMUMWIDTH

Description

Allows the source to define the minimum width (X-axis) that the source can acquire.

Source

The minimum width that the device can scan. This may be different depending on the value of CAP_FEEDERENABLED.

Values

Type: TW_FIX32






Required By

None


See Also

CAP_FEEDERENABLEDICAP_PHYSICALWIDTHICAP_UNITS


Chapter 10

ICAP_NOISEFILTER

Description

For devices that support noise filtering. This capability selects the algorithm used to remove noise.

Source



Values

Type: TW_UINT16

Default Value: TWNF_NONE

Allowed Values: TWNF_NONETWNF_AUTOTWNF_LONEPIXELTWNF_MAJORITYRULE




Required By

None


None


ICAP_ORIENTATION

Description

Defines which edge of the “paper” the image’s “top” is aligned with. This information is used to adjust the frames to match the scanning orientation of the paper. For instance, if an ICAP_SUPPORTEDSIZE of TWSS_ISOA4 has been negotiated, and ICAP_ORIENTATION is set to TWOR_LANDSCAPE, then the Source must rotate the frame it downloads to the scanner to reflect the orientation of the paper. Please note that setting ICAP_ORIENTATION does not affect the values reported by ICAP_FRAMES; it just causes the Source to use them in a different way.

The upper-left of the image is defined as the location where both the primary and secondary scans originate. (The X axis is the primary scan direction and the Y axis is the secondary scan direction.) For a flatbed scanner, the light bar moves in the secondary scan direction. For a handheld scanner, the scanner is drug in the secondary scan direction. For a digital camera, the secondary direction is the vertical axis when the viewed image is considered upright.

Application

If one pivots the image about its center, then orienting the image in TWOR_LANDSCAPE has the effect of rotating the original image 90 degrees to the “left.” TWOR_PORTRAIT mode does not rotate the image. The image may be oriented along any of the four axes located 90 degrees from the unrotated image. Note that:

TWOR_ROT0 == TWOR_PORTRAIT and TWOR_ROT270 == TWOR_LANDSCAPE.TWOR_AUTO orients the image according to criteria determined by the source. TWOR_AUTOTEXT orients the document using text only algorithms. TWOR_AUTOPICTURE orients the document using image only algorithms.

Source

The Source is responsible for rotating the image if it allows this capacity to be set.


Values

Type: TW_UINT16

Default Value: TWOR_PORTRAITAllowed Values: TWOR_ROT0

TWOR_ROT90TWOR_ROT180TWOR_ROT270TWOR_PORTRAIT (equals TWOR_ROT0)TWOR_LANDSCAPE (equals TWOR_ROT270)TWOR_AUTO // 2.0 and higherTWOR_AUTOTEXT // 2.0 and higherTWOR_AUTOPICTURE // 2.0 and higher



Chapter 10



Required By

None


None

See Also

ICAP_ROTATIONICAP_AUTOSIZE


ICAP_OVERSCAN

Description

Overscan is used to scan outside of the boundaries described by ICAP_FRAMES, and is used to help acquire image data that may be lost because of skewing.

Consider the following:

This is primarily of use for transport scanners which rely on edge detection to begin scanning. If overscan is supported, then the device is capable of scanning in the inter-document gap to get the skewed image information.

Application

Use this capability, if available, to help software processing images for deskew and border removal.

Source



Values

Type: TW_UINT16

Default Value: TWOV_NONE

Allowed Values: TWOV_NONETWOV_AUTOTWOV_TOPBOTTOMTWOV_LEFTRIGHTTWOV_ALL




FramePaper Overscan


Chapter 10

Required By

None


None


ICAP_PATCHCODEDETECTIONENABLED

Description

Turns patch code detection on and off.

Source

Support this capability if the scanner supports any patch code recognition. If the device allows this feature to be turned off, then default to off. If the device does not support disabling this feature, report TRUE and disallow attempts to set FALSE.



Values

Type: TW_BOOL






Required By

None


None

See Also

ICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODEMAXSEARCHPRIORITIESICAP_PATCHCODESEARCHPRIORITIESICAP_PATCHCODESEARCHMODEICAP_PATCHCODEMAXRETRIESICAP_PATCHCODETIMEOUT


Chapter 10

ICAP_PATCHCODEMAXRETRIES

Description

Restricts the number of times a search will be retried if none are found on each page.

Application

Refine this capability to limit the number of times the patch code search algorithm is retried on a page that contains no patch codes.

Source

If supported, limit the number of retries the value specified.



Values

Type: TW_UINT32






Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODEMAXSEARCHPRIORITIESICAP_PATCHCODESEARCHPRIORITIESICAP_PATCHCODESEARCHMODEICAP_PATCHCODETIMEOUT


ICAP_PATCHCODEMAXSEARCHPRIORITIES

Description

The maximum number of supported search priorities.

Application

Query this value to determine how many patch code detection priorities can be set.

Source

Set this value to limit the number of priorities to speed the detection process.

If patch code searches can be prioritized, report the maximum number of priorities allowed for a search.



Values

Type: TW_UINT32






Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODESEARCHPRIORITIESICAP_PATCHCODESEARCHMODE


Chapter 10

ICAP_PATCHCODEMAXRETRIESICAP_PATCHCODETIMEOUT


ICAP_PATCHCODESEARCHMODE

Description

Restricts patch code searching to certain orientations, or prioritizes one orientation over the other.

Application

Negotiate this capability if the orientation of patch codes is already known to the application. Refinement of this capability can speed the patch code search.

Source

If set then apply the specified refinements to future patch code searches.



Values

Type: TW_UINT16


Allowed Values: TWBD_HORZTWBD_VERT TWBD_HORZVERTTWBD_VERTHORZ




Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODEMAXSEARCHPRIORITIESICAP_PATCHCODESEARCHPRIORITIES


Chapter 10

ICAP_PATCHCODEMAXRETRIESICAP_PATCHCODETIMEOUT


ICAP_PATCHCODESEARCHPRIORITIES

Description

A prioritized list of patch code types dictating the order in which patch codes will be sought.

Application

Set this capability to specify the order and priority for patch code searching. Refining the priorities to only the patch code types of interest to the application can speed the search process.

Source

If this type of search refinement is supported, then report the current values.

If set, then limit future searches to the specified patch codes in the specified priority order.



Values

Type: TW_UINT16


Allowed Values: TWPCH_PATCH1TWPCH_PATCH2TWPCH_PATCH3TWPCH_PATCH4TWPCH_PATCH6TWPCH_PATCHT


Container for MSG_SET: TW_ ARRAY


Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODEMAXSEARCHPRIORITIES


Chapter 10

ICAP_PATCHCODESEARCHMODEICAP_PATCHCODEMAXRETRIESICAP_PATCHCODETIMEOUT


ICAP_PATCHCODETIMEOUT

Description

Restricts the total time spent on searching for a patch code on each page.

Application

Refine this value to tune the length of time the search algorithm is allowed to execute before giving up.

Source

If supported, limit the duration of a patch code search to the value specified.



Values

Type: TW_UINT32






Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_PATCHCODEMAXSEARCHPRIORITIESICAP_PATCHCODESEARCHPRIORITIESICAP_PATCHCODESEARCHMODEICAP_PATCHCODEMAXRETRIES


Chapter 10

ICAP_PHYSICALHEIGHT

Description

The maximum physical height (Y-axis) the Source can acquire (measured in units of ICAP_UNITS).

Source

For a flatbed scanner, the scannable height of the platen. For a handheld scanner, the maximum length of a scan.

For dimensionless devices, such as digital cameras, this ICAP is meaningless for all values of ICAP_UNITS other than TWUN_PIXELS. If the device is dimensionless, the Source should return a value of zero if ICAP_UNITS does not equal TWUN_PIXELS. This tells the application to inquire with TWUN_PIXELS.

Note: The physical acquired area may be different depending on the setting of CAP_FEEDERENABLED (if the Source has separate feeder and non-feeder acquire areas).


Values

Type: TW_FIX32






Required By

All Image Sources



See Also

CAP_FEEDERENABLEDICAP_UNITS


ICAP_PHYSICALWIDTH

Description

The maximum physical width (X-axis) the Source can acquire (measured in units of ICAP_UNITS).

Source

For a flatbed scanner, the scannable width of the platen. For a handheld scanner, the maximum width of a scan.

For dimensionless devices, such as digital cameras, this ICAP is meaningless for all values of ICAP_UNITS other than TWUN_PIXELS. If the device is dimensionless, the Source should return a value of zero if ICAP_UNITS does not equal TWUN_PIXELS. This tells the application to inquire with TWUN_PIXELS. The Source should then reply with its X-axis pixel count.

Note: The physical acquired area may be different depending on the setting of CAP_FEEDERENABLED (if the Source has separate feeder and non-feeder acquire areas).


Values

Type: TW_FIX32






Required By

All Image Sources



See Also

CAP_FEEDERENABLEDICAP_UNITS


Chapter 10

ICAP_PIXELFLAVOR

Description

Sense of the pixel whose numeric value is zero (minimum data value). For example, consider a black and white image:

If ICAP_PIXELTYPE is TWPT_BW then If ICAP_PIXELFLAVOR is TWPF_CHOCOLATE then Black = 0 Else if ICAP_PIXELFLAVOR is TWPF_VANILLA then White = 0

Application

Sources may prefer a different value depending on ICAP_PIXELTYPE. Set ICAP_PIXELTYPE and do a MSG_GETDEFAULT to determine the Source’s preferences.

Source

TWPF_CHOCOLATE means this pixel represents the darkest data value that can be generated by the device (the darkest available optical value may measure greater than 0).

TWPF_VANILLA means this pixel represents the lightest data value that can be generated by the device (the lightest available optical value may measure greater than 0).

Values

Type: TW_UINT16

Default Value: TWPF_CHOCOLATE





Required By

All Image Sources



See Also

ICAP_PIXELTYPE


ICAP_PIXELFLAVORCODES

Description

Used only for CCITT data compression. Specifies whether the compressed codes’ pixel “sense” will be inverted from the Current value of ICAP_PIXELFLAVOR prior to transfer.

Source


Values

Type: TW_UINT16

Default Value: TWPF_CHOCOLATE





Required By

None


None

See Also

ICAP_COMPRESSION


Chapter 10

ICAP_PIXELTYPE

Description

The type of pixel data that a Source is capable of acquiring (for example, black and white, gray, RGB, etc.).

Application

• MSG_GET returns a list of all pixel types available from the Source.

• MSG_SET on a TW_ENUMERATION structure requests that the Source restrict the available pixel types to the enumerated list.

• MSG_SET on a TW_ONEVALUE container specifies the only pixel type the application can accept.

If the application plans to transfer data through any mechanism other than Native and cannot handle all possible ICAP_PIXELTYPEs, it must support negotiation of this ICAP.

Source


Values

Type: TW_UINT16


Allowed Values: TWPT_BWTWPT_GRAYTWPT_RGBTWPT_PALETTETWPT_CMYTWPT_CMYKTWPT_YUVTWPT_YUVKTWPT_CIEXYZTWPT_LABTWPT_SRGBTWPT_SRGB64TWPT_BGRTWPT_CIELABTWPT_CIELUVTWPT_YCBCRTWPT_INFRARED





Required By

All Image Sources



See Also

ICAP_BITDEPTHICAP_BITDEPTHREDUCTION


Chapter 10

ICAP_PLANARCHUNKY

Description

Allows the application and Source to identify which color data formats are available. There are two options, “planar” and “chunky.”

For example, planar RGB data is transferred with the entire red plane of data first, followed by the entire green plane, followed by the entire blue plane (typical for three-pass scanners). “Chunky” mode repetitively interlaces a pixel from each plane until all the data is transferred (R-G-B-R-G-B…) (typical for one-pass scanners).

Source


Values

Type: TW_UINT16


Allowed Values: TWPC_CHUNKYTWPC_PLANAR




Required By

All Image Sources



See Also

TW_IMAGEINFO.Planar


ICAP_ROTATION

Description

How the Source can/should rotate the scanned image data prior to transfer. This doesn’t use ICAP_UNITS. It is always measured in degrees. Any applied value is additive with any rotation specified in ICAP_ORIENTATION.

Source


Values

Type: TW_FIX32

Default Value: 0

Allowed Values: +/- 360 degrees




Required By

None


None

See Also

ICAP_ORIENTATIONICAP_AUTOSIZE


Chapter 10

ICAP_SHADOW

Description

Specifies which value in an image should be interpreted as the darkest “shadow.” All values “darker” than this value will be clipped to this value.

Application

Whether darker values are smaller or larger can be determined by examining the Current value of ICAP_PIXELFLAVOR.

Source

If more or less than 8 bits are used to describe the image, the actual data values should be normalized to fit within the 0-255 range. The normalization need not result in a homogeneous distribution if the original distribution was not homogeneous.


Values

Type: TW_FIX32

Default Value: 0





Required By

None


None

See Also

ICAP_PIXELFLAVOR


ICAP_SUPPORTEDBARCODETYPES

Description

Provides a list of bar code types that can be detected by the current Data Source.

Application

Query this capability to determine if the Data Source can detect bar codes that are appropriate to the particular application.

Source

If bar code detection is supported, report all the bar code types that can be detected.



Values

Type: TW_UINT16


Allowed Values: TWBT_3OF9TWBT_2OF5INTERLEAVEDTWBT_2OF5NONINTERLEAVEDTWBT_CODE93TWBT_CODE128TWBT_UCC128TWBT_CODABARTWBT_UPCATWBT_UPCETWBT_EAN8TWBT_EAN13TWBT_POSTNETTWBT_PDF417TWBT_2OF5INDUSTRIALTWBT_2OF5MATRIXTWBT_2OF5DATALOGICTWBT_2OF5IATATWBT_3OF9FULLASCIITWBT_CODABARWITHSTARTSTOPTWBT_MAXICODE





Chapter 10

Required By

None


None

See Also

ICAP_BARCODEDETECTIONENABLEDICAP_SUPPORTEDPATCHCODETYPESICAP_BARCODEMAXSEARCHPRIORITIESICAP_BARCODESEARCHPRIORITIESICAP_BARCODESEARCHMODEICAP_BARCODEMAXRETRIESICAP_BARCODETIMEOUT


ICAP_SUPPORTEDEXTIMAGEINFO

Description

Lists all of the information that the Source is capable of returning from a call to DAT_EXTIMAGEINFO.

Application

This capability mirrors CAP_SUPPORTEDCAPS. The array indicates all of the possible TWEI_ values the Source is capable of returning. It does not guarantee that all of these values will be returned for every call to DAT_EXTIMAGEINFO, because that depends on the negotiated capabilities and on what the device finds.

For instance, if the Source supports CAP_BARCODEDETECTIONABLED, then it may report TWEI_BARCODETEXT as part of this capability. However, if the image that was just captured has no barcode data, then the Source can return TWRC_INFONOTSUPPORTED for that TW_INFO field, when the Application calls DAT_EXTIMAGEINFO.

Source

The Source lists all of the TWEI_ values it is capable of returning in a call to DAT_EXTIMAGEINFO.

Values

Type: TW_UINT16

Default Value: Same as the current value

Allowed Values: An array of TWEI_* values



Required By

None



See Also

DAT_EXTIMAGEINFO, ICAP_EXTIMAGEINFO


Chapter 10

ICAP_SUPPORTEDPATCHCODETYPES

Description

A list of patch code types that may be detected by the current Data Source.

Application

Query this capability to determine if the Data Source can detect patch codes that are appropriate to the Application.

Source

If patch code detection is supported, report all the possible patch code types that might be detected.



Values

Type: TW_UINT16


Allowed Values: TWPCH_PATCH1TWPCH_PATCH2TWPCH_PATCH3TWPCH_PATCH4TWPCH_PATCH6TWPCH_PATCHT

Container for MSG_GET: TW_ARRAYTW_ONEVALUE



Required By

None


None

See Also

ICAP_PATCHCODEDETECTIONENABLEDICAP_PATCHCODEMAXSEARCHPRIORITIESICAP_PATCHCODESEARCHPRIORITIES


ICAP_PATCHCODESEARCHMODEICAP_PATCHCODEMAXRETRIESICAP_PATCHCODETIMEOUT


Chapter 10

ICAP_SUPPORTEDSIZES

Description

For devices that support fixed frame sizes. Defined sizes match typical page sizes. This specifies the size(s) the Source can/should use to acquire image data.

(*) Constant should not be used in Sources or Applications using TWAIN 1.8 or higher. For instance, use TWSS_A4 instead of TWSS_A4LETTER (note that the values are the same, the reason for the new constants is to improve naming clarification and consistency).

Note: TWSS_B has been removed from the specification.

Source

The frame size selected by using this capability should be reflected in the TW_IMAGELAYOUT structure information.

If the Source cannot acquire the exact frame size specified by the application, it should provide the closest possible size (preferably acquiring an image that is larger than the requested frame in both axes).

For devices that support physical dimensions TWSS_NONE indicates that the maximum image size supported by the device is to be used. Devices that do not support physical dimensions should not support this capability.

Note: TWSS_MAXSIZE has been added to simplify negotiating for the entire acquisition area of a device, since TWSS_NONE was overloaded to mean both “a custom frame” and “the maximum image size.”



Values

Type: TW_UINT16


Allowed Values: TWSS_NONE*TWSS_A4LETTER*TWSS_B5LETTERTWSS_USLETTERTWSS_USLEGALTWSS_A5*TWSS_B4*TWSS_B6TWSS_USLEDGERTWSS_USEXECUTIVETWSS_A3


*TWSS_B3*TWSS_A6TWSS_C4TWSS_C5TWSS_C6

// 1.8 AdditionsTWSS_4A0TWSS_2A0TWSS_A0TWSS_A1TWSS_A2TWSS_A4 TWSS_A4LETTERTWSS_A7TWSS_A8TWSS_A9TWSS_A10TWSS_ISOB0TWSS_ISOB1TWSS_ISOB2TWSS_ISOB3 TWSS_B3TWSS_ISOB4 TWSS_B4TWSS_ISOB5TWSS_ISOB6 TWSS_B6TWSS_ISOB7TWSS_ISOB8TWSS_ISOB9TWSS_ISOB10TWSS_JISB0TWSS_JISB1TWSS_JISB2TWSS_JISB3TWSS_JISB4TWSS_JISB5 TWSS_B5LETTERTWSS_JISB6TWSS_JISB7TWSS_JISB8TWSS_JISB9TWSS_JISB10TWSS_C0TWSS_C1TWSS_C2TWSS_C3TWSS_C7TWSS_C8TWSS_C9TWSS_C10TWSS_USSTATEMENTTWSS_BUSINESSCARDTWSS_MAXSIZE



Chapter 10



Required By

All Image Sources that support fixed frame sizes.


MSG_GET/CURRENT/DEFAULT, MSG_SET/RESET

See Also

ICAP_FRAMESICAP_AUTOSIZETW_IMAGEINFOTW_IMAGELAYOUT


ICAP_THRESHOLD

Description

Specifies the dividing line between black and white. This is the value the Source will use to threshold, if needed, when ICAP_PIXELTYPE = TWPT_BW.

The value is normalized so there are no units of measure associated with this ICAP.

Application

Application will typically set ICAP_BITDEPTHREDUCTION to TWBR_THRESHOLD to use this capability.

Source

Source should fit available values linearly into the defined range such that the lowest available value equals 0 and the highest equals 255.


Values

Type: TW_FIX32

Default Value: 128





Required By

None


None

See Also



Chapter 10

ICAP_TILES

Description

This is used with buffered memory transfers. If TRUE, Source can provide application with tiled image data.

Application

If set to TRUE, the application expects the Source to supply tiled data for the upcoming transfer(s). This persists until the application sets it to FALSE. If the application sets it to FALSE, Source will supply strip data.

Source

If Source can supply tiled data and application does not set this ICAP, Source may or may not supply tiled data at its discretion.

In State 6, ICAP_TILES should reflect whether tiles or strips will be used in the upcoming transfer.


Values

Type: TW_BOOL






Required By

None


None

See Also

TW_IMAGEMEMXFER


ICAP_TIMEFILL

Description

Used only with CCITT data compression. Specifies the minimum number of words of compressed codes (compressed data) to be transmitted per line.

Source


Values

Type: TW_UINT16

Default Value: 1


Container for MSG_GET: TW_ONEVALUETW_RANGE



Required By

None


None

See Also

ICAP_COMPRESSION


Chapter 10

ICAP_UNDEFINEDIMAGESIZE

Description

If TRUE the Source will issue a MSG_XFERREADY before starting the scan.

Note: The Source may need to scan the image before initiating the transfer. This is the case if the scanned image is rotated or merged with another scanned image.

Application

Used by the application to notify the Source that the application accepts -1 as the image width or -length in the TW_IMAGEINFO structure.

Source


Values

Type: TW_BOOL






Required By

None


None

See Also

TW_IMAGEINFO


ICAP_UNITS

Description

Unless a quantity is dimensionless or uses a specified unit of measure, ICAP_UNITS determines the unit of measure for all quantities.

Application

Applications should be able to handle TWUN_PIXELS if they want to support data transfers from “dimensionless” devices such as digital cameras.

Source


Values

Type: TW_UINT16

Default Value: TWUN_INCHES

Allowed Values: TWUN_INCHESTWUN_CENTIMETERSTWUN_PICASTWUN_POINTSTWUN_TWIPSTWUN_PIXELSTWUN_MILLIMETERS




Required By

All Image Sources



See Also

ICAP_FRAMESDAT_IMAGELAYOUT


Chapter 10

ICAP_XFERMECH

Description

Allows the application and Source to identify which transfer mechanisms the source supports.

Application

The current value of ICAP_XFERMECH must match the data argument type when starting the transfer using the triplet: DG_IMAGE / DAT_IMAGExxxxXFER / MSG_GET.

Values

Type: TW_UINT16

Default Value: TWSX_NATIVE

Allowed Values: TWSX_NATIVETWSX_FILETWSX_MEMORYTWSX_FILE2TWSX_MEMFILE




Required By

All Image Sources



See Also

DG_IMAGE / DAT_IMAGExxxxXFER / MSG_GET


ICAP_XNATIVERESOLUTION

Description

The native optical resolution along the X-axis of the device being controlled by the Source. Most devices will respond with a single value (TW_ONEVALUE).

This is NOT a list of all resolutions that can be generated by the device. Rather, this is the resolution of the device’s optics. Measured in units of pixels per unit as defined by ICAP_UNITS (pixels per TWUN_PIXELS yields dimensionless data).

Source


Values

Type: TW_FIX32


Allowed Values: >0




Required By

None


None

See Also

ICAP_UNITSICAP_XRESOLUTIONICAP_YNATIVERESOLUTION


Chapter 10

ICAP_XRESOLUTION

Description

All the X-axis resolutions the Source can provide.

Measured in units of pixels per unit as defined by ICAP_UNITS (pixels per TWUN_PIXELS yields dimensionless data). That is, when the units are TWUN_PIXELS, both ICAP_XRESOLUTION and ICAP_YRESOLUTION shall report 1 pixel/pixel. Some data sources like to report the actual number of pixels that the device reports, but that response is more appropriate in ICAP_PHYSICALHEIGHT and ICAP_PHYSICALWIDTH.

Application

Setting this value will restrict the various resolutions that will be available to the user during acquisition.

Applications will want to ensure that the values set for this ICAP match those set for ICAP_YRESOLUTION.

Source


Values

Type: TW_FIX32


Allowed Values: >0




Required By

All Image Sources




See Also

ICAP_UNITSICAP_XNATIVERESOLUTIONICAP_YRESOLUTION


Chapter 10

ICAP_XSCALING

Description

All the X-axis scaling values available. A value of ‘1.0’ is equivalent to 100% scaling. Do not use values less than or equal to zero.

Application

Applications will want to ensure that the values set for this ICAP match those set for ICAP_YSCALING. There are no units inherent with this data as it is normalized to 1.0 being “unscaled.”

Source


Values

Type: TW_FIX32

Default Value: 1.0

Allowed Values: > 0




Required By

None


None

See Also

ICAP_YSCALING


ICAP_YNATIVERESOLUTION

Description

The native optical resolution along the Y-axis of the device being controlled by the Source.

Measured in units of pixels per unit as defined by ICAP_UNITS (pixels per TWUN_PIXELS yields dimensionless data).

Application

Most devices will respond with a single value (TW_ONEVALUE). This is NOT a list of all resolutions that can be generated by the device. Rather, this is the resolution of the device’s optics

Source


Values

Type: TW_FIX32


Allowed Values: > 0




Required By

None


None

See Also

ICAP_UNITSICAP_XNATIVERESOLUTIONICAP_YRESOLUTION


Chapter 10

ICAP_YRESOLUTION

Description

All the Y-axis resolutions the Source can provide.

Measured in units of pixels per unit as defined by ICAP_UNITS (pixels per TWUN_PIXELS yields dimensionless data). That is, when the units are TWUN_PIXELS, both ICAP_XRESOLUTION and ICAP_YRESOLUTION shall report 1 pixel/pixel. Some data sources like to report the actual number of pixels that the device reports, but that response is more appropriate in ICAP_PHYSICALHEIGHT and ICAP_PHYSICALWIDTH.

Application

Setting this value will restrict the various resolutions that will be available to the user during acquisition.

Applications will want to ensure that the values set for this ICAP match those set for ICAP_XRESOLUTION.

Source


Values

Type: TW_FIX32


Allowed Values: > 0




Required By

All Image Sources




See Also

ICAP_UNITSICAP_XRESOLUTIONICAP_YNATIVERESOLUTION


Chapter 10

ICAP_YSCALING

Description

All the Y-axis scaling values available. A value of ‘1.0’ is equivalent to 100% scaling. Do not use values less than or equal to zero.

There are no units inherent with this data as it is normalized to 1.0 being “unscaled.”

Application

Applications will want to ensure that the values set for this ICAP match those set for ICAP_XSCALING.

Source


Values

Type: TW_FIX32

Default Value: 1.0

Allowed Values: > 0




Required By

None


None

See Also

ICAP_XSCALING


ICAP_ZOOMFACTOR

Description

When used with MSG_GET, return all camera supported lens zooming range.

Application

Use this capability with MSG_SET to select one of the lens zooming value that the Source supports.

Source



Values

Type: TW_INT16

Default Value: 0

Allowed Values: Source dependent.

Container for MSG_GET: TW_ENUMERATION,TW_ONEVALUE,TW_RANGE



Required By

None. Highly recommended for digital cameras that are equipped with zoom lenses.


MSG_GET, MSG_SET,MSG_GETCURRENT, MSG_RESET


Chapter 10


11Return Codes and Condition Codes

Chapter ContentsAn Overview of Return Codes and Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-1Currently Defined Return Codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2Currently Defined Condition Codes. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-2Custom Return and Condition Codes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11-4

An Overview of Return Codes and Condition CodesThe TWAIN protocol defines no dynamic messaging system through which the application might determine, in real-time, what is happening in either the Source Manager or a Source. Neither does the protocol implement the native messaging systems built into the operating environments that TWAIN is defined to operate under (Microsoft Windows and Macintosh). This decision was made due to issues regarding platform specificity and higher-than-desired implementation costs.

Instead, for each call the application makes to DSM_Entry( ), whether aimed at the Source Manager or a Source, the Source Manager returns an appropriate Return Code (TWRC_xxxx). The Return Code may have originated from the Source if that is where the original operation was destined.

To get more specific status information, the application can use the DG_CONTROL / DAT_STATUS / MSG_GET operation to inquire the complimentary Condition Code (TWCC_xxxx) from the Source Manager or Source (whichever one originated the Return Code).

The application should always check the Return Code. If the Return Code is TWRC_FAILURE, it should also check the Condition Code. This is especially important during capability negotiation.

There are very few, if any, catastrophic error conditions for the application to worry about. Usually, the application will only have to “recover” from low memory errors caused from allocations in the Source. Most error conditions are handled by the Source Manager or, most typically, by the Source (often involving interaction with the user). If the Source fails in a way that is unrecoverable, it will ask to have its user interface disabled by sending the MSG_CLOSEDSREQ to the application’s event loop.


Chapter 11

The following operations can only return TWRC_SUCCESS or TWRC_FAILURE / TWCC_SEQERROR, if called in the wrong state. This is to avoid a situation where an Application is unable to shutdown a Source because of an error state, like the device being offline. The Source must comply with the request to change states.

DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFERDG_CONTROL / DAT_PENDINGXFERS / MSG_RESETDG_CONTROL / DAT_USERINTERFACE / MSG_DISABLEDSDG_CONTROL / DAT_IDENTITY / MSG_CLOSEDSDG_CONTROL / DAT_IDENTITY / MSG_CLOSEDSM

When an Application receives this condition code, it alerts the user (so they can exit, if they wish). While waiting for the user response the Application polls the value of CAP_DEVICEONLINE. The device continues to be offline as long as this call returns TWCC_SUCCESS, with a value of FALSE.

The state 3 operation DG_CONTROL / DAT_IDENTITY / MSG_OPENDS is the only one capable of returning TWCC_CHECKDEVICEONLINE. The Application cannot check CAP_DEVICEONLINE (since that is a state 4 operation), however, it can retry the MSG_OPENDS call, if it chooses.

Currently Defined Return Codes

Currently Defined Condition CodesThe following are the currently defined condition codes:

Code Description

TTWRC_CANCEL Abort transfer or the Cancel button was pressed.

TWRC_CHECKSTATUS Partially successful operation; request further information.

TWRC_DSEVENT Event (or Windows message) belongs to this Source.

TWRC_ENDOFLIST No more Sources found after MSG_GETNEXT.

TWRC_FAILURE Operation failed - get the Condition Code for more information.

TWRC_NOTDSEVENT Event (or Windows message) does not belong to this Source.

TWRC_SUCCESS Operation was successful.

TWRC_XFERDONE All data has been transferred.


Code Description

TWCC_BADCAP* Capability not supported by Source or operation (get, set) is not supported on capability, or capability had dependencies on other capabilities and cannot be operated upon at this time (Obsolete, see TWCC_CAPUNSUPPORTED, TWCC_CAPBADOPERATION, and TWCC_CAPSEQERROR).

TWCC_BADDEST Unknown destination in DSM_Entry.

TWCC_BADPROTOCOL Unrecognized operation triplet.

TWCC_BADVALUE Data parameter out of supported range.

TWCC_BUMMER General failure. Unload Source immediately.

TWCC_CAPBADOPERATION* Operation (i.e., Get or Set) not supported on capability.

TWCC_CAPSEQERROR* Capability has dependencies on other capabilities and cannot be operated upon at this time.

TWCC_CAPUNSUPPORTED* Capability not supported by Source.

TWCC_CHECKDEVICEONLINE Check the device status using CAP_DEVICEONLINE, this condition code can be returned by any TWAIN operation in state 4 or higher, or from the state 3 DG_CONTROL / DAT_IDENTITY / MSG_OPENDS. The state remains unchanged. If in state 4 the Application can poll with CAP_DEVICELINE until the value returns TRUE.

TWCC_DAMAGEDCORNER Operation failed because the document has a damaged corner.

TWCC_DENIED File System operation is denied (file is protected).

TWCC_DOCTOODARK Operation failed because the document is too dark.

TWCC_DOCTOOLIGHT Operation failed because the document is too light.

TWCC_FILEEXISTS Operation failed because file already exists.

TWCC_FILENOTFOUND File not found.

TWCC_FOCUSERROR Operation failed because of a focusing error during document capture.

TWCC_INTERLOCK Operation failed because the cover or door is open.

TWCC_LOWMEMORY Not enough memory to complete operation.

TWCC_MAXCONNECTIONS Source is connected to maximum supported number of applications.

TWCC_NODS Source Manager unable to find the specified Source.

TWCC_NOMEDIA Source has nothing to capture for a transfer. Can be returned by DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS, by any of the DAT_IMAGE*XFER operations, by DAT_IMAGEINFO or DAT_EXTIMAGEINFO.

TWCC_NOTEMPTY Operation failed because directory is not empty.


Chapter 11

* TWCC_BADCAP has been replaced with three new condition codes that more clearly specify the reason for a capability operation failure. For backwards compatibility applications should also accept TWCC_BADCAP and treat it as a general capability operation failure. No 1.6 Image Data Sources should return this condition code, but use the new ones instead.

Custom Return and Condition CodesAlthough probably not necessary or desirable, it is possible to create custom Return Codes and Condition Codes. Refer to the TWAIN.H file for the value of TWRC_CUSTOMBASE for custom Return Codes and TWCC_CUSTOMBASE for custom Condition Codes. All custom values must be numerically greater than these base values. Remember that the consumer of these custom values will look in your TW_IDENTITY.ProductName field to clarify what the identifier’s value means. There is no other protection against overlapping custom definitions.

TWCC_OPERATIONERROR Source or Source Manager reported an error to the user and handled the error; no application action required.

TWCC_PAPERDOUBLEFEED Transfer failed because of a feeder error, this can be returned by any of the DAT_IMAGE*XFER operations. When received the current TWAIN state remains unchanged.

TWCC_PAPERJAM Transfer failed because of a feeder error, this can be returned by any of the DAT_IMAGE*XFER operations. When received the current TWAIN state remains unchanged.

TWCC_SEQERROR Illegal operation for current Source Manager or Source state.

TWCC_SUCCESS Operation worked.

Code Description


ATWAIN Articles

Chapter Contents Device Events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-1Supported Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-5Automatic Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-8Camera Preview. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-9Internationalization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-19Audio Snippets. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-19How to use the Preview Device. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-21Imprinter / Endorser. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-23Capability Ordering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-24Defaults . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A-30

The articles in this appendix provide additional information about some of the features described in this specification.

Device EventsTWAIN 1.8 expands upon asynchronous event notification. Previous versions provided the DG_CONTROL / DAT_NULL messages: MSG_CLOSEDSOK, MSG_CLOSEDSREQ and MSG_XFERREADY to permit the Source to alert the Application that it needed to exit, or that an image was ready to be processed. With the addition of Digital Cameras, and the burgeoning interest in Push Technologies, it has become desirable to enhance TWAIN in this area.

An event begins when the Source needs to alert the Application to some change that has occurred within the device. For example, the owner of a Digital Camera (which is tethered to a host machine) has changed the setting for flash from on to off. The Source wants to alert the Application of this change: first, it records the event in a FIFO queue; second, it sends a DG_CONTROL / DAT_NULL / DAT_DEVICEEVENT to the Source Manager, which forwards the message to the Application.

TWAIN 2.1 Specification A-1

Chapter A

The Application receives the DG_CONTROL / DAT_NULL / DAT_DEVICEEVENT, and immediately issues a DG_CONTROL / DAT_DEVICEEVENT / MSG_GET request to the Source. The Source delivers the information about the event, and pops it off the queue. The process concludes with the Application examining the information and acting upon it, in this case by alerting the user that the flash setting on the camera has been changed.

Notes:

• Sources must start up in a mode with device events turned off (an empty array for CAP_DEVICEEVENTS), this is for the benefit of pre-1.8 applications which may not be able to process this new event.

• Device events are never generated by an Application setting a value within a Source (such as Application changing ICAP_FLASHUSED2). Device events are only generated in response to some outside change within the Source or the Device (such as the User changing the flash setting on the camera).

• Sources must maintain an internal Event Queue, so that they can report each and every device event to the Application in the order of their occurrence.

• Device events are supported in State 4. Windows Sources must use the main window handle supplied with the DG_CONTROL / DAT_PARENT / MSG_OPENDS if they issue device events in State 4. In States 5 through 7 Sources must use the pTW_USERINTERFACE->hParent supplied in the DG_CONTROL / DAT_USERINTERFACE / MSG_ENABLEDS triplet.

• Since device events may occur in State 4, Applications that enable them using CAP_DEVICEEVENTS must be ready to receive and process them.

• When the Application receives a device event, it must immediately collect the information about it. The Application must not issue the DG_CONTROL / DAT_DEVICEEVENT / MSG_GET, except when it has received a DG_CONTROL / DAT_NULL / DAT_DEVICEEVENT message.

• The Application must process events without User intervention, this is to prevent situations where the device event queue builds up because a User is not responding to the system.

• Applications may sometimes fail to respond to a Source’s device events. A maximum queue size should be selected so that the Source does not exhaust memory. If the queue fills, the Source must do the following:

• Turns off device events (resets CAP_DEVICEEVENT to an empty array).

• Refuse to set CAP_DEVICEEVENT until the queue is emptied, return TWCC_SEQERROR.

• Process DG_CONTROL / DAT_DEVICEEVENT / MSG_GET requests for each item on the device event queue.

After the last device event is read by the Application, return TWRC_FAILURE / TWCC_DEVICEEVENTOVERFLOW for the next call to DG_CONTROL / DAT_DEVICEEVENT / MSG_GET.

• After TWCC_DEVICEEVENTOVERFLOW has been reported, permit the Source to set CAP_DEVICEEVENT again.

A-2 TWAIN 2.1 Specification

Figure A-1 Device Events

Source

FlashON OFF

FlashOFF

Event Queue

SourceManager

Application

Display:Flash ON

Step 1: The Source senses that the device has changed from ON to OFF and stores thisinformation in an Event Queue. A Queue must be used because the Source maygenerate multiple events before the Application can respond.

Source

FlashOFF

Event Queue

SourceManager

Application

Display:Flash ON

DG_CONTROL /DAT_NULL /MSG_DEVICEEVENT

FlashOFF

Step 2: The Source sends a DG_CONTROL / DAT_NULL / MSG_DEVICEEVENT to theApplication. The Application only knows that some Event has taken place.

Source

FlashOFF

Event Queue

SourceManager

Application

Display:Flash ON

DG_CONTROL/DAT_DEVICEEVENTMSG_GET

FlashOFF

FlashOFF

Step 3: The Application sends a DG_CONTROL / DAT_DEVICEEVENT / MSG_GET tothe Source to learn about the Event. The Source informs the Application that theflash is OFF and it clears the Event from its Queue.

Source

(empty)

Event Queue

SourceManager

Application

FlashOFF

Display:Flash OFF

FlashOFF

Step 4: The Application informs the User that the flash is now OFF.


Chapter A

This section details the various event types and how Sources and Applications should make use of them.

TWDE_CHECKAUTOMATICCAPTUREThe automatic capture settings on the device have been changed.

TWDE_CHECKBATTERYStatus of the battery has changed. Sources will report BatteryMinutes or BatteryPercentage depending on which capabilities say they support.

TWDE_CHECKDEVICEONLINEThe device has been powered off. If an Application receives this device event, it should call CAP_DEVICEONLINE to verify the state of the Source, and then proceed as seems appropriate.

TWDE_CHECKFLASHThe flash setting on the device has been changed.

TWDE_CHECKPOWERSUPPLYThe power supply has changed, for example this event would be generated if AC was removed from a device, putting it on battery. Scanners may also provide this event to notify that a power on reset has taken place, indicating that the device has been power cycled.

TWDE_CHECKRESOLUTIONThe resolution on the device has changed.

TWDE_DEVICEADDEDA device has been added to the Source. See DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY and DG_CONTROL / DAT_FILESYSTEM / MSG_GETINFO to get more information about the new device.

TWDE_DEVICEOFFLINEA device has become unavailable. This is different from TWDC_DEVICEREMOVED, since the device is assumed to be connected.

TWDE_DEVICEREADYA device is ready to capture another image. Applications should be careful when negotiating this event, especially in situations where images are gathered quickly, as with automatic capture.

TWDE_DEVICEREMOVEDA device has been removed from the Source. This is different from TWDE_DEVICEOFFLINE. As soon as this event is received an Application should re-negotiate its current device, since that may have been the one that was removed. Sources must default to the TWFY_CAMERA device if the current device is removed.

TWDE_PAPERDOUBLEFEEDReport double feeds to the Application. Because of the asynchronous nature of device events there may still be images waiting to be transferred, applications need to decide if they want to recover these images or discard them.


TWDE_PAPERJAMReport paper jams to the Application. Because of the asynchronous nature of device events there may still be images waiting to be transferred, applications need to decide if they want to recover these images or discard them.

Supported SizesTypical uses for ICAP_SUPPORTEDSIZES include, but are not limited to the following:

The following table details the physical dimensions associated with ICAP_SUPPORTEDSIZES. Multiply millimeters by 0.03937 to get the approximate inches. Multiply inches by 25.4 to get the approximate millimeters.

A0, A1 Technical drawings, posters

A2, A3 Drawings, diagrams, large tables

A4 Letters, magazines, forms, catalogs, laser printer and copying machine output

A5 Note pads

A6 Postcards

B5, A5, B6, A6 Books

C4, C5, C6 Envelopes for A4 letters: unfolded (C4), folded once (C5), folded twice (C6)

B4, A3 Newspapers, supported by most copying machines in addition to A4


Chapter A

ICAP_SUPPORTEDSIZES Description

TWSS_NONE Images will match the maximum scanning dimensions of the device. This setting is only applicable to devices that have fixed measurable dimensions, such as most scanners. Devices that do not support physical dimensions should not support ICAP_SUPPORTEDSIZES.

TWSS_A4LETTER

TWSS_B5LETTER

TWSS_B3

TWSS_B4

TWSS_B6

These values are preserved for backward compatibility. TWAIN 1.8+ enabled Applications should not use these settings.

TWSS_B This value is obsolete, and no longer supported by the specification. Do not use it.

TWSS_USLETTER 8.5” x 11.0” (216mm x 280mm)

TWSS_USLEGAL 8.5” x 14.0” (216mm x 356mm)

TWSS_USLEDGER 11.0” x 17.0” (280mm x 432mm)

TWSS_USEXECUTIVE 7.25” x 10.5” (184mm x 267mm)

TWSS_USSTATEMENT 5.5” x 8.5” (140mm x 216mm)

TWSS_BUSINESSCARD 90mm x 55mm

TWSS_4A0 1682mm x 2378mm

TWSS_2A0 1189mm x 1682mm

TWSS_A0 841mm x 1189mm








TWSS_A8 52mm x 74mm

TWSS_A9 37mm x 52mm


TWSS_ISOB0 1000mm x1414mm


TWSS_ISOB1 707mm x1000mm

TWSS_ISOB2 500mm x 707mm









TWSS_JISB0 1030mm x1456mm

TWSS_JISB1 728mm x1030mm

TWSS_JISB2 515mm x 728mm









TWSS_C0 917mm x1297mm

TWSS_C1 648mm x 917mm







TWSS_C8 57mm x 81mm

TWSS_C9 40mm x 57mm


Chapter A

Automatic CaptureAutomatic image capture is intended for Digital Cameras, although there may be opportunities for other kinds of devices. The intention is to allow an Application to control when pictures are taken, how many pictures are taken, and the interval of time between picture taking. All that is required is that the device be able to perform capture on command from the Source, the timing control and storage of pictures may reside in the Source or the device; the Application does not care.

There are three capabilities needed to control automatic capture:

• CAP_AUTOMATICCAPTURE

• CAP_TIMEBEFOREFIRSTCAPTURE

• CAP_TIMEBETWEENCAPTURES

And one triplet:

• DG_CONTROL/DAT_FILESYSTEM/MSG_AUTOMATICCAPTUREDIRECTORY

CAP_AUTOMATICCAPTURE selects the number of images to be captured. A value of zero (0), the default, disables it. CAP_TIMEBEFOREFIRSTCAPTURE selects how many milliseconds are to pass before the first picture is taken by the device. If this value is 0, then picture taking begins immediately. CAP_TIMEBETWEENCAPTURES selects the milliseconds of elapsed time between pictures. If this value is 0, then the pictures are taken as fast as the device can go.

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIRECTORY selects the directory that will receive the images as they are captured.

Automatic capture expects the device (or Source) to manage the storage of images until the Application is ready to collect them. Applications may choose to retrieve images as they are captured by the Source (using the DAT_FILESYSTEM triplets to browse the storage directory), but must realize that this may affect the performance of the device.

The nature of automatic capture suggests that an Application should be able to disconnect from a Source and expect that if it returns after CAP_TIMEBEFOREFIRSTCAPTURE has passed, there may be images available for it to collect. Because of this Sources should remember their automatic capture settings from session to session, so that a Source starting up does not inadvertently clear them.

Applications need to remember that since the capture of images may occur outside of their control that the settings may be changed directly on the device by the user, resulting in alternations in any of the automatic capture settings. Applications that cannot support this uncertainty should clear the Source’s automatic capture settings prior to shutdown (and after notifying the User).



Camera PreviewSome digital cameras offer a way to preview the intended shot through either a continuous flow of low-resolution frames or streaming video. TWAIN exposes two methods for a Source to present this information to an Application, both in association with the TWFY_CAMERAPREVIEW device.

The TWFY_CAMERAPREVIEW Device

Sources that wish to provide access to their preview camera must do so through DAT_FILESYSTEM. A minimum configuration includes a single TWFY_CAMERA and a single TWFY_CAMERAPREVIEW. The Application discovers what devices are available by using the DAT_FILESYSTEM commands MSG_GETFIRSTFILE and MSG_GETNEXTFILE. It can then switch from the startup default TWFY_CAMERA to the TWFY_CAMERAPREVIEW using the MSG_CHANGEDIRECTORY command.

Performance

It is important when taking a picture from preview mode that the switch from TWFY_CAMERAPREVIEW to TWFY_CAMERA happens as quickly as possible. Applications can minimize the switch over time by negotiating the settings of the TWFY_CAMERA before changing to the TWFY_CAMERAPREVIEW device to collect real-time images.

Sources can help by optimizing their communication with the TWFY_CAMERA, perhaps downloading its values when the user sends MSG_ENABLEDS to the TWFY_CAMERAPREVIEW device so that when the switch back occurs all that needs to happen is a command sent to the camera to take a picture.

Another matter of importance is the transfer mechanism. If the camera is capable of sending a run of continuous snapshots to the application (as opposed to real video streaming), then it is recommended that the TWFY_CAMERAPREVIEW device only support an ICAP_XFERMECH of TWSX_NATIVE.

Entering Preview Mode

An application should do the following before entering preview mode.

1. The application sends MSG_OPENDS to the Source.

2. The application determines that the Source TWFY_CAMERAPREVIEW device.

3. The user/application negotiates values for the TWFY_CAMERA device.

4. The user/application decides to enter preview mode. The application uses MSG_CHANGEDIRECTORY to change to the TWFY_CAMERAPREVIEW device.

5. The application uses MSG_ENABLEDS to enter preview mode. Note that the value of ShowUI should depend on which of the next two sections the application decides to use to control the Source (GUI mode or programmatic).

Previewing with the Source’s GUI (ShowUI == TRUE)

If the application relies solely on the Source’s GUI for its control of the camera, then it shouldn’t have to worry about preview mode issues, since it is hoped that a Source that supports preview


Chapter A

will provide access to it from its GUI. This section is concerned with a more limited area, where an application has opted to control the Source programmatically, except for the use of preview. One reason an application might need to do this is to provide preview support for cameras that output streaming video. TWAIN does not have a mechanism for handling this kind of data, so if the only way that a TWAIN application will be able to show this kind of preview data, is if the Source provides a GUI that can show it.

If the Source has CAP_CAMERAPREVIEWUI set to TRUE, then it is possible for the application to use this to preview the images coming from the camera. In this mode the application does not have to concern itself with the kind of data that the Source is providing, since the Source takes the responsibility of displaying the preview images to the user. However, the application does have to wait for the triggers that indicates that the user wishes to take a picture, or that they wish to exit from preview mode. To help standardize this behavior, the preview GUI should be able to indicate two things.

1. Take a picture – if the user selects to take a picture, perhaps by pressing a button labeled CAPTURE, then the Source should send the DAT_NULL command MSG_CLOSEDSOK back to the application.

2. Cancel preview – if the user decides to exit from preview mode, then the Source should send the DAT_NULL command MSG_CLOSEDSREQ back to the application. The application should then send MSG_DISABLEDS to the Source, change back to the TWFY_CAMERA device, and resume its programmatic control of the Source.

Previewing under Programmatic Control (ShowUI == FALSE):

TWAIN provides programmatic support for TWFY_CAMERAPREVIEW devices that operate by taking a continuous flow of low-resolution snapshots. An application learns that a Source is capable of this by changing to TWFY_CAMERAPREVIEW and testing ICAP_XFERMECH. If the capability is supported, then the TWFY_CAMERAPREVIEW device is capable of transferring these low-resolution images fast enough to simulate real-time video. The way the application obtains these images is similar to how scanners work. The application sets CAP_XFERCOUNT to –1 and enables the Source. The Source sends a MSG_XFERREADY to the application, and the application begins transferring and displaying the low-resolution images as fast as it can. These steps are repeated to aid understanding…

1. The application negotiates any capabilities with the TWFY_CAMERAPREVIEW device, including setting CAP_XFERCOUNT to –1, indicating that the application wishes to receive an unlimited number of images.

2. The application send MSG_ENABLEDS (ShowUI == FALSE) to the Source.

3. The Source sends back MSG_XFERREADY and transitions to State 6.

4. The application uses MSG_IMAGENATIVEXFER to transfer the image and the Source transitions to State 7.

5. The application displays the image.

6. The application uses DAT_PENDINGXFERS / MSG_ENDXFER to transition the Source to State 6. The application needs to pay attention to the TW_PENDINGXFERS.Count, but it is expected that it should remain at –1.

7. Go to step (4).

As long as the application and Source are looping from steps (4) through (7) the application should be displaying a continuous run of snapshots.


Since the application is in complete control, it is implementation dependent on how the user indicates that a picture should be taken. However, once the decision to take a picture is made, the steps to do it are as follows…

Taking a Picture:

The application should do the following when it is told to take a picture while in preview mode.

1. The application sends DAT_PENDINGXFERS / MSG_ENDXFER to the Source, transitioning from State 7 to State 6 (if necessary).

2. The application sends DAT_PENDINGXFERS / MSG_RESET to the Source, transitioning from State 6 to State 5.

3. The application sends MSG_DISABLEDS to the Source, transitioning from State 5 to State 4.

4. The application uses MSG_CHANGEDIRECTORY to switch from the TWFY_CAMERAPREVIEW device to the TWFY_CAMERA device.

5. The application uses MSG_ENABLEDS (ShowUI == FALSE) to enable the TWFY|_CAMERA device.

6. The application sends one of the MSG_IMAGExxxxXFER commands to the Source.

7. The source takes the full resolution picture and transfers it back to the application

File SystemThis section consists of the following:

• Overview

• Rules for path and file names

• File system components

• Rule for root directory

• Rules for image directory

• File Types

• DAT_FILESYSTEM operations

• Thumbnails and Sound snippets

• Context variable

• Condition Codes

Note: The term ‘camera’ is used generically in the specification to describe a device that captures an image, and is not limited to just devices that employ a camera to accomplish this.


Chapter A

Overview

Digital cameras and some scanners have the ability to capture images to their own local storage. When Automatic Capturing is being used an Application need not collect the captured images until long after their acquisition. A file system is a good representation for the storage of images (since it is a model that is familiar to most programmers), so TWAIN exposes a simple file system interface that Applications may browse through in a random fashion.

There is also a need in TWAIN to expose multiple devices through a single Source. Single pass duplex scanners have multiple cameras that accept different settings. Digital cameras come with disks and memory expansion cards, and many are able to provide a stream of preview images. The file system offers a way for a Source to maintain in its root directory a list of the devices available to an Application.

Rules for Path and File Names

There are two main grouping of files supported by TWAIN; devices, which are associated with real-time capture, which accept image capture settings, and which are of the form:

/DeviceName

And image path and file names, which are images on local storage which have been previously captured by the device, and which are of the form (bracketed items are optional):

[/DomainName] [/HostName] /TopDirectory [/Sub-Directory…] /ImageFile

1. A filename consists of any characters except: NUL (0), either of the slashes ‘/’ or ‘\’ and the colon ‘:’.

2. Sources should at a minimum support the characters: “A-Z a-z 0-9 _ .”

3. The file system should not be case sensitive, though it may show upper and lowercase.

4. Applications should take into consideration that internationalized Sources may construct filenames from characters within UNICODE.

5. The forward slash ‘/’ and backward slash ‘\’ may be used interchangeably in the creation of path names. Sources and Applications must support the use of both slashes. (ex: /abc\xyz).

6. Multiple adjacent slashes reduce to a single slash. (ex: ///\\abc///xyz == /abc/xyz).

7. The root directory is designated as a solitary slash (ex: / or \).

8. The MSG_CHANGEDIRECTORY and MSG_AUTOMATICCAPTUREDIRECTORY operations are the only ones that accepts absolute or relative directory paths. All other operations occur within the current directory.

9. MSG_CHANGEDIRECTORY and MSG_AUTOMATICCAPTUREDIRECTORY can use dot ‘.’ to address the current directory (ex: ./abc).

10. MSG_CHANGEDIRECTORY and MSG_AUTOMATICCAPTUREDIRECTORY can use dot-dot ‘..’ to address the parent directory (ex: ../abc).

11. In the root directory a MSG_CHANGEDIRECTORY or AUTOMATICCAPTUREDIRECTORY to dot-dot ‘..’ is the same as dot ‘.’ (ex: /. == /..).

Examples:\Camera is the same as /Camera


//Camera is the same as /Camera./Camera is the same as /Camera../Camera is the same as /Camera

File System Components

A file system consists of the following.

1. A root directory.

2. A camera device (TWFY_CAMERA), which must be the default device when the Source starts.

3. Zero or more additional devices (TWFY_CAMERATOP, TWFY_CAMERATOP, TWFY_CAMERAPREVIEW).

4. It is possible for a Source to support multiples of a given device type, for instance a scanner may support two devices of type TWFY_CAMERA, both with a supporting TWFY_CAMERATOP and TWFY_CAMERABOTTOM. Use pTW_FILESYSTEM->DeviceGroupMask to uniquely identify a camera or to group it with its associated top and bottom cameras. For example:

5. Zero or more directories for storing images (on memory cards, disks, etc…). These are organized in a hierarchical structure that permits, but does not require the ability to browse in a network:

Sources that provide image storage must provide at least one TWFY_DIRECTORY. TWFY_DOMAIN and TWFY_HOST are optional.

Rules for Root Directory1. The root directory can only contain devices or directories, not images.

2. The application cannot create, delete, copy into or rename files in the root directory.

3. Files in a directory are not ordered in any fashion (for instance, an Application may not assume that they are alphabetically sorted). There is one exception to this rule: when an Application issues a DG_CONTROL / DAT_FILESYSTEM / MSG_GETFIRSTFILE on the root directory, the Source must return a TWFY_CAMERA device. This device is the designated default capture camera. If an Application begins capability negotiation, or image capture without accessing DAT_FILESYSTEM, then this is the device that will be used.

Name Type Group/camera_1 TWFY_CAMERA 0x0001

/camera_1_top TWFY_CAMERATOP 0x0001

/camera_1_bottom TWFY_CAMERABOTTOM 0x0001

/camera_2 TWFY_CAMERA 0x0002

/camera_2_top TWFY_CAMERATOP 0x0002

/camera_2_bottom TWFY_CAMERABOTTOM 0x0002

A TWFY_DOMAIN directory contains only TWFY_HOST directories

A TWFY_HOST directory contains only TWFY_DIRECTORY directories

A TWFY_DIRECTORY contains TWFY_IMAGE files and/or TWFY_DIRECTORY directories.


Chapter A

Rules for Image Directory1. A TWFY_DIRECTORY can contain 0 or more TWFY_DIRECTORYs (sub-directories).

2. Can contain 0 or more TWFY_IMAGE (image files).

3. May be fully accessible, read or write protected.

4. May be created or deleted by an Application, given that it is not in the root directory, and that it is not protected by the Source.

Context Variable

The reason for the Context variable is that it allows for unconditional mingling of DAT_FILESYSTEM operations. If there was no Context variable, then Applications would be more limited in the order of operations that could be performed. For instance, the recursive directory walk in the code sample would be much harder to accomplish without a Context to help the Source identify the current directory being accessed by a call to MSG_GETNEXTFILE.

This value is provided solely for the benefit of Source writers. When MSG_GETFIRSTFILE is called, the Source should record the current directory and the current file and store those values internally, using Context as a reference to their location. The nature or value of the Context is dependent on the implementation of the Source, Applications must never attempt to use or modify the Context. A call to MSG_GETINFO must use this Context to identify the file being reported. Calls to any of the file transfer methods (MSG_IMAGENATIVEXFER, MSG_IMAGEFILEXFER, MSG_IMAGEMEMXFER, MSG_AUDIONATIVEXFER, MSG_AUDIOFILEXFER) must use this Context to determine the data being sent to the Application. A call to MSG_GETNEXTFILE must use this Context to help obtain the next file from the directory (this will result in a change in the context as it references the new file). And, finally, a call to MSG_GETCLOSE releases the memory in the Source associated with this Context.

Condition Codes

These are some condition codes that apply specifically to file system operations:

TWCC_DENIED File system operation is denied. A Source should report this condition code if an attempt is made to access a protected file. Examples of such protection include: any attempt to delete, rename or copy into the root directory; protected files that are on the network; and any file that the Source feels it needs to protect.

TWCC_FILEEXISTS The operation failed because the file already exists. A Source should report this condition code if an attempt is made to create a sub-directory with a name that already exists in the targeted directory; or if an attempt is made to copy or rename over an existing file or directory.

TWCC_FILENOTFOUND The file was not found. This can occur for a variety of reasons: attempts to change directory to a path that does not exist; attempts to delete, rename or copy files that do not exist; as the condition code from MSG_GETFIRSTFILE for an empty directory; or MSG_GETNEXTFILE when it finds no more files in the current directory; and, finally, from MSG_GETINFO if it is requested to provide information on a file that has been deleted.


TWCC_NOTEMPTY Operation failed because the directory is not empty. This condition code is used by the Source if an attempt is made with the Recursion flag set to FALSE to delete a non-empty directory.

File Types

The DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY operation is used to make either a device or a directory current. If a camera device is the target, then all capability negotiation is with that device and all images come from that device, until a new MSG_CHANGEDIRECTORY command is issued. If an image directory is selected then the current device is set to be the root level directory name (i.e., changing to /abc/mno/xyz means that the current device is /abc).

TWFY_CAMERA Every TWAIN file system must support at least one camera, which must be the default device on startup. This is for compatibility with pre 1.8 applications as well as post 1.8 applications that do not choose to make use of the file system. On single pass duplex scanners, this camera device is used to simultaneously set values for the top and bottom cameras. During the capturing of images (in duplex mode) it sends a stream of images in the order: TOP, BOTTOM, TOP…

TWFY_CAMERATOP / TWFY_CAMERABOTTOM

Single pass duplex scanners may opt to provide independent access to the top and bottom cameras. A device with one of these file types controls the settings for the specified camera. If this device is the current device at the time image capture commences, then only images from that camera will be passed to the Application. This means that even if a device is set for duplex scanning, if the current device has a file type of TWFY_CAMERATOP, then only top images will be passed to the Application.

TWFY_CAMERAPREVIEW A logical device that performs camera live preview functionality. When implementing the Source for this logical device, related capabilities must be negotiated to perform preview specific functions. Among them, ICAP_XRESOLUTION and ICAP_YRESOLUTION must be implemented to specify the preview image sizes. Other capabilities may be available in some sources, such as ICAP_ZOOMFACTOR and ICAP_FLASHUSED2.


Chapter A

TWFY_DIRECTORY At the root directory level files of this type should correspond to a physical piece of hardware (a memory card or a disk). The root directory is only allowed to contain devices. Sub-directories may only contain image files or more sub-directories. Access to files and directories is controlled by the Source, so Applications should check all operations and watch out for condition codes such as TWCC_DENIED.

TWFY_IMAGE Any directory, except root, may contain image files. The DAT_FILESYSTEM messages MSG_GETFIRSTFILE and MSG_GETNEXTFILE select the current image. Once an image has been selected, it may be transferred in the same fashion used to acquire images from a camera. Note: this file type is reserved for full resolution images, see the section on Thumbnails for information on how to acquire them.

DAT_FILESYSTEM Operations

MSG_AUTOMATICCAPTUREDIRECTORY

Selects the directory to be used to store images acquired by automatic capture.

MSG_CHANGEDIRECTORY

Selects the device or image subdirectory. Use this to select between direct camera (scanner) control, and browsing of stored images. All capabilities negotiated and triplet operations are with the current device (directory), until this value is changed by the Application.

MSG_COPY Copies the specified file from one directory to another. If the Recursive flag is TRUE and the file type specified is TWFY_DIRECTORY then that directory and all the files and directories under it are copied. The Application cannot copy files into the root directory.

MSG_CREATEDIRECTORY

Creates a new image subdirectory. The Application cannot create files in the root directory.

MSG_DELETE Deletes the specified file. If the Recursive flag is TRUE and the file type specified is TWFY_DIRECTORY, then all the files under that directory are deleted. The Application cannot delete files in the root directory.

MSG_FORMATMEDIA Formats the currently selected storage device. Use with caution.


MSG_GETCLOSE Closes the Context created by MSG_GETFIRSTFILE.

MSG_GETFIRSTFILE Creates a Context that points to the first file in a directory. This Context is used by MSG_GETINFO, MSG_GETNEXTFILE, MSG_GETCLOSE; and for files of type TWFY_IMAGE all image transfer related operations performed in states 6 and 7 use the image pointed to by this Context (i.e., DAT_IMAGEINFO, DAT_IMAGEMEMXFER, etc…).

MSG_GETINFO Returns information about a device, directory or image file.

MSG_GETNEXTFILE Updates the Context to point to the next file in the directory.

MSG_RENAME Renames a directory or an image file. If the directories differ, then it moves the file as well, creating it in the new location and deleting it from the old location. Files in the root directory cannot be renamed by the Application.

Thumbnails and Sound Snippets

TWAIN is primary concerned with the acquisition of images, so the file system does not contain thumbnail files or sound files, since these kinds of data are expected to be associated with image files. This simplifies an Application’s browsing of the file system, since it need only concern itself with one type of data file (TWFY_IMAGE), and does not have to trace associated data files.

Sources must filter out non-image files, if the device stores thumbnail and sound data independent of the image files. For instance, if a device stores the following files:

IMAGE001.TIF

IMAGE001_THUMBNAIL.TIF

IMAGE001_SOUND.WAV

The file system must only report the existence of IMAGE001.TIF

An Application obtains the thumbnail for an image by setting ICAP_THUMBNAILSENABLED to TRUE; the same filename is used for both the full resolution and thumbnail versions of an image. By setting ICAP_THUMBNAILSENABLED, the Application decides which version of the image it receives.

Sound snippets are also associated with image files, unlike thumbnails it is possible for a single image file to own several sound snippets. An Application can get the number of snippets that an image owns, and then, during image transfer, the Application has the option to transfer any number of those snippets. It is also possible to collect the snippets for an image without transferring the image data.

Sample Recursive Directory Walk

The following is a sample recursive directory walk.

// This Application function walks through all the files in a Source’s

// file system, counting the file types file system, counting the file


Chapter A

// types it finds. It is intended only as a sample, error checking is

// omitted to simplify the code.

typedef struct {

int Devices;

int Directories;

int Images;

} t_Counters;

TW_UINT16 DirectoryWalk(TW_FILESYSTEM *fsArg, t_Counters *Counters)

{

TW_UINT16 rc; TW_FILESYSTEM fs;

// Caller has set fsArg->InputFile to some value, such as “/”…

rc = (*DS_Entry) (&app,&src,DG_CONTROL,DAT_FILESYSTEM, MSG_CHANGEDIRECTORY, fsArg);

// We do GETFIRSTFILE first in each new directory, GETNEXTFILE for all

// subsequent calls…

for (rc = (*DS_Entry)(&app,&src,DG_CONTROL,DAT_FILESYSTEM, MSG_GETFIRSTFILE,&fs); rc == TWRC_SUCCESS;

rc = (*DS_Entry)(&app,&src,DG_CONTROL,DAT_FILESYSTEM ,MSG_GETNEXTFILE,&fs)) {

// Count the appropriate file type…

switch (fs.FileType) {

default: Counters->Devices += 1; break;

case TWFY_IMAGE: Counters->Images += 1; break; case TWFY_DOMAIN:

case TWFY_HOST:

case TWFY_DIRECTORY: Counters->Directories += 1;

// Recursively step into this directory, looking for more

// stuff…

rc = DirectoryWalk(&fs,&Counters);

if (rc != TWRC_SUCCESS) {

rc = (*DS_Entry)(&app,&src,DG_CONTROL,DAT_FILESYSTEM, MSG_GETCLOSE,&fs);

return(rc);

}

break;

}

}


// Cleanup and return…

rc = (*DS_Entry)(&app,&src,DG_CONTROL,DAT_FILESYSTEM,MSG_GETCLOSE,&fs); return(TWRC_SUCCESS);

}

// Using this function…

TW_UINT16 rc;

TW_FILESYTEM fs;

t_Counters Counters;

memset(&fs,0,sizeof(fs));

memset(&Counters,0,sizeof(Counters));

strcpy(fs.InputFile,”/”); // start at root…

rc = DirectoryWalk(&fs,&Counters);

InternationalizationTWAIN 2.0 Applications and Sources use UTF-8 to pass localized data back and forth in any field with a type of TW_STR32, TW_STR64, TW_STR128 or TW_STR255. Since the first 128 characters map to US-ASCII, this requires no change for most Applications and Sources.

Some structures should never localize their data, like TW_IDENTITY, since changing locales presents a problem for Applications and Sources that need to recognize a particular string to help with customization.

The use of UTF-8 is not mandated for localized strings displayed by the Application or the Source. Those strings are internal to their respective functions, and do not pass through the TWAIN API, so the Applications and Sources are free to encode them in any way they choose.

Audio SnippetsDigital Cameras have the ability to acquire audio snippets along with an image. To support this TWAIN 1.8 provides a new data group, DG_AUDIO. Because TWAIN is image-centric, DG_AUDIO operations are dependent on an image context, audio snippets must be associated with an image. When a Source enters into state 6, the Application can opt to transfer any and all audio snippets. The steps required to obtain audio snippets deliberately parallel the steps required to transfer images, to reduce the effort to learn how to access this new kind of data.

The following Data Argument Types (DATs) are supported by DG_AUDIO:

DAT_AUDIOFILEXFER transfer audio in file format

DAT_AUDIOINFO info about an audio snippet

DAT_AUDIONATIVEXFER transfer audio in native format


Chapter A

The following DG_CONTROL (DATs) are supported when DAT_XFERGROUP is set to DG_AUDIO, DATs not mentioned in this list must return TWRC_FAILURE / TWCC_BADPROTOCOL:

DAT_CAPABILITY no changes to its operation

DAT_EVENT no changes to its operation

DAT_IDENTITY no changes to its operation

DAT_NULL no changes to its operation

DAT_PASSTHRU no changes to its operation

DAT_PENDINGXFERS reports number of snippets remaining to be transferred, MSG_ENDXFER and MSG_RESET do not cause the Source to drop to State 5.

DAT_SETUPFILEXFER selects the audio file format

DAT_STATUS no changes to its operation

DAT_USERINTERFACE no changes to its operation

DAT_XFERGROUP MSG_SET, MSG_GETDEFAULT and MSG_GETCURRENT added to allow switching between data groups. The default value for MSG_GETDEFAULT must be DG_IMAGE. And when the Source starts up, MSG_GETCURRENT must report DG_IMAGE as the current data group, to maintain compatibility with pre-TWAIN 1.8 Applications.

The following capabilities support audio; all capabilities are negotiable at all times (at least in state 4), independent of the current setting of DAT_XFERGROUP:

ACAP_XFERMECH negotiate audio snippet transfer mechanism

Collecting Audio Snippets

The transfer of an audio snippet was designed to be used when an Application is browsing through a selection of stored images. There is nothing to prevent the transfer of audio when an image is captured in real-time, though TWAIN does require that any audio snippets be transferred before the image is transferred.

A typical transfer may occur in the following way: An Application is browsing through storage managed by the TWAIN Source using MSG_GETFILEFIRST / MSG_GETFILENEXT (see DAT_FILESYSTEM), and finds an image that it wants to work with. The Application enters state 6 by calling DG_CONTROL / DAT_IDENTITY / MSG_ENABLEDS. If the Application wants to find out if there are any audio snippets associated with the image, it can call DG_AUDIO / DAT_AUDIOINFO / MSG_GET. In this example it finds in the TW_AUDIOINFO structure that this image file has three audio snippets associated with it. The Application wants the second audio snippet, so it calls DG_CONTROL / DAT_XFERGROUP / MSG_SET and sets the data group to DG_AUDIO. This call changes the context of the Source, it is now set up to transfer audio data. One effect of this is that a call to DG__CONTROL / DAT_PENDINGXFERS / MSG_GET will report the number of audio snippets (for this image) that remain to be transferred. Because the Application wants the second audio snippet, it must discard the first one, and does this by making a call to DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER. The snippet that it wants is now available to be transferred, and it does this with a call to DG_AUDIO / DAT_AUDIONATIVEXFER / MSG_GET. The Source moves up into state 7. The Application ends the transfer with a call to DG_CONTROL / DAT_PENDINGXFERS / MSG_ENDXFER.


Because the Application only wanted the second audio snippet, it can return to DG_IMAGE by making a call to DG_CONTROL / DAT_XFERGROUP / MSG_SET. Once this is done, all other commands work in a traditional TWAIN fashion. The Application can opt to transfer or discard the image, even though it did not transfer all of the audio snippets.

There is one more thing to note, if the Application had read the third audio snippet, or if it had issued the DG_CONTROL / DAT_PENDINGXFERS / MSG_RESET command while in DG_AUDIO, the state of the Source would remain at state 6. TWAIN works this way because it is image-centric, the only way to transition from state 6 to state 5 is when it is determined that there are no more images to transfer.

Notes1. TWAIN 1.8 supports native and file transfers of audio snippets. Buffered mode transfers

are not supported, because TWAIN does not have the necessary infrastructure to describe audio data, and it was decided that adding that structure in this release would be overly complex, and probably incomplete.

2. As a general rule, even though many operations are possible with DAT_XFERGROUP set to DG_AUDIO, Applications are encouraged to only change to DG_AUDIO for the length of time it takes to collect an audio snippet, and to stay in DG_IMAGE mode at all other times.

3. Though TWAIN is image-centric, it is possible to envision a TWAIN Source that is only capable of supporting DG_AUDIO. The TWAIN Working Group feels that any such notion is a bad idea, and encourages anyone thinking of doing this to pick on some other API.

How to use the Preview Device

Application Switch to the Preview Logical Device

The application first tries to switch to the preview logical device using the DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY triplet with TWFY_CAMERAPREVIEW set in InputName field of TW_FILENAME structure. If the returned value is TW_SUCCESS, the application can proceed.

1. After the application successfully switches to the preview device, all subsequent capability negotiation is with the preview device.

2. The application queries the Source with capability CAP_CAMERAPREVIEWUI. If it returns SUCCESS, then the Source is able to assume the responsibility of displaying preview images. The application can choose to use the Source’s UI or not when it issues the MSG_ENABLEDS. If the application uses the Source’s UI, it will do nothing but wait to issue MSG_DISABLEDS, or wait for a MSG_CLOSEDSREQ from the Source to stop the preview mode. If the application does not use the Source’s UI or the Source does not provide a UI, then the application should follow the following steps.

Setting Up Environments for Preview Mode1. The application starts negotiation on the Preview size using the ICAP_XRESOLUTION and

ICAP_YRESOLUTION capabilities with MSG_GET first. With the returned supported sizes


Chapter A

from the Source, the application can set the selected preview sizes using the ICAP_XRESOLUTION and ICAP_YRESOLUTION capabilities with MSG_SET.

2. Optionally, the application can negotiate the zoom lens value, camera flash state during previewing, etc, with available capabilities such as ICAP_ZOOMFACTOR, ICAP_FLASHUSED2. If application queries for capabilities that are not related to preview device, Source will return TWRC_FAILURE.

Start Getting and Displaying Preview Thumbnails1. The application can use the automatic capture feature with CAP_XFERCOUNT to -1

(Application is willing to transfer multiple images).

2. Application issues MSG_ENABLEDS to move to state 5. Upon receiving this message, the Source should start capturing images1.

3. Source issues MSG_XFERREADY, indicating that an image is present, and state moves to 6.

LOOP:

4. Application issues DAT_IMAGENATIVEXFER to get image and goes to state 7.

5. Application issues MSG_ENDXFER to return to state 6, and it displays the image. Then if it wants the next preview image, examines pTW_PENDINGXFERS->Count to verify that there is another image, and it goes to LOOP. Source, upon receiving the MSG_ENDXFER message, takes the next picture and returns -1 in the pTW_PENDINGXFERS->Count.

END LOOP

6. If the application wants to end preview mode, it issues DAT_PENDINGXFERS / MSG_RESET. This forces the Source to go to state 5 (CAP_XFERCOUNT is set to 0). If the Source is unable to deliver preview images, it sets pTW_PENDINGXFERS->Count to 0 in reply to the application’s MSG_ENDXFER command, and returns to state 5.

7. The application can then issue MSG_DISABLEDS, which returns it to state 4, and now the application can use DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY to change directory to the camera device to take a full resolution picture.

How to Take a Snapshot from Preview Scene1. The application could provide a button or menu item for the user to take a snapshot from

the preview scene, for example, a “Take Picture” button. In response to this, the application should use the triplet DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRECTORY with TWFS_CAMERA set in the TW_FILENAME structure to stop the preview mode.

2. Subsequently, the application can use the automatic capture feature with CAP_XFERCOUNT to 1, CAP_TIMEBEFOREFIRSTCAPTURE to 0 and CAP_AUTOMATICCAPTURE set to 1 to initiate the capture of preview snapshot.

3. When the Source receives the CAP_AUTOMATICCAPTURE, it should capture the preview snapshot, and inform the application with MSG_XFERREADY when it is ready to transfer.

4. After receiving the MSG_XFERREADY, the application should use one of the three standard image transfer methods to transfer the captured image from the Source to the application.

1. The Source takes a picture as soon as it receives MSG_ENABLEDS and each time it receives MSG_ENDXFER


5. At the end of this operation, the application has the option of going back to the preview thumbnail loop.

Imprinter / EndorserScanners intended for document imaging sometimes include accessories that let the scanner print data on the documents as it scans them. TWAIN provides basic functionality to negotiate capabilities for imprinter / endorser devices. An imprinter is a general term for any document-printing device. An endorser is more specialized, and is primarily intended as proof of scanning. In addition to the type of printing device, TWAIN offers ways to locate the printer on the scanning path: top or bottom of the sheet of paper, before or after the paper has been scanned. It is the responsibility of the Source to provide the available combinations to the Application. It is the responsibility of the Application to enable the printers that it wants to use, and to establish seed values prior to scanning.

This is a context sensitive scheme, Applications use CAP_PRINTER to discover what printers are available to the Source, and to select each of those printers for negotiation.

CAP_PRINTERENABLED determines whether or not a given printer will be used when scanning begins; a value of TRUE indicates that it will be used, a value of FALSE that it will not be used. Applications must enable a printer before negotiating the seed values.

CAP_PRINTERINDEX describes an index that counts by ones for every image seen by a given printer.

CAP_PRINTERMODE selects one of three options: print one line of text from CAP_PRINTERSTRING, or multiple lines from CAP_PRINTERSTRING, or a compound string constructed (in order) from CAP_PRINTERSTRING, CAP_PRINTERINDEX and CAP_PRINTERSUFFIX.

CAP_PRINTERSTRING specifies the base message to be printed. For compound strings, the CAP_PRINTERSTRING serves as the prefix to the CAP_PRINTERINDEX.

CAP_PRINTERSUFFIX is only available for compound strings, and describes the text (if any) that is to follow the CAP_PRINTERINDEX.

Example of Use:

Consider a Source that supports two CAP_PRINTERs:

TWPR_IMPRINTERTOPBEFORE

TWPR_IMPRINTERBOTTOMBEFORE

The Application then:

• uses CAP_PRINTER to discover the two printers

• sets CAP_PRINTER to TWPR_IMPRINTERTOPBEFORE

• sets CAP_PRINTERENABLED to TRUE (turning this printer on)


Chapter A

• sets CAP_PRINTERMODE to TWPM_SINGLESTRING

• sets CAP_PRINTERSTRING to a string containing today’s date

• sets CAP_PRINTER to TWPR_IMPRINTERBOTTOMBEFORE

• sets CAP_PRINTERENABLED to FALSE (turning this printer off)

Note that the value of CAP_PRINTER is not important at the time of scanning, it is the other capabilities that control the imprinter, like CAP_PRINTERENABLED; CAP_PRINTER only selects the current printer under negotiation.

Capability OrderingAs the number of capabilities described by TWAIN has increased it has become clear that there are dependencies between many of them. In some cases these dependencies are not likely to be critical, for example if ICAP_CCITTKFACTOR is set to some non-zero value, and ICAP_COMPRESSION is not TWCP_GROUP32D, most scanners will not see this as a problem. On the other hand, if ICAP_COMPRESSION is set to TWCP_JPEG and ICAP_XFERMECH is set to TWSX_NATIVE then it is extremely unlikely that the Application will get useable image data.

It is the responsibility of the Source to properly constrain itself according to the current settings of all of its capabilities. Doing so has the following benefits:

• The Source protects itself from illegal configurations.

• The Source reports to the Application through constraints and the TWCC_CAPSEQERROR condition code which capabilities are fully, partially or currently not negotiable.

It is the responsibility of the Application to negotiate capabilities in the proper order. Doing so has the following benefits:

• The Application protects itself from illegal configurations.

• The Application can use constraints and occurrences of TWCC_CAPSEQERROR to modify the behavior of its user interface, better representing the Source’s capabilities to the user.

The reset of this article is written in the order of negotiation that an Application should use to control a Source.

Language Support

The first thing the Source and Application should negotiate is the language. This negotiation best occurs as part of the DG_CONTROL / DAT_PARENT / MSG_OPENDS call. The Application reports the language it is using in appIdentity->Version.Language. The Source should attempt to try to match this language. If it cannot, it should attempt to match the language that the user logged in with. If this fails then is should pick the best language that it can. For those Sources that support CAP_LANGUAGE the Application has a further opportunity to try and get a good language match, and this should be done as soon as the Source is successfully opened.


Duplex Control

If an Application finds that CAP_DUPLEX exists and it indicates that duplex scanning is supported, then the Application should negotiate CAP_DUPLEXENABLED. If CAP_DUPLEXENABLED is set to FALSE, then DAT_FILESYSTEM capable Sources should not report any TWFY_CAMERABOTTOM devices in the root directory. If the Source is set to a TWFY_CAMERABOTTOM device at the time that CAP_DUPLEXENABLED is set to FALSE, then it should automatically change itself to the corresponding TWFY_CAMERATOP device.

Device Negotiation

If the Source supports DAT_FILESYSTEM, then the Application needs to walk through the root directory to determine what devices are available, if it wants to independently control the individual devices. Sources are required to default to the TWFY_CAMERA device (the implied default for Sources that do not support DAT_FILESYSTEM). If an Application negotiates capabilities using this device, then the Source is expected to apply the settings to as many of its applicable devices as possible. For instance, in a duplex scanner changing the value of ICAP_BRIGHTNESS for the default TWFY_CAMERA device will change the settings of its corresponding TWFY_CAMERATOP and TWFY_CAMERABOTTOM. Once the list of devices has been identified, the Application may optionally change to one of them using DG_CONTROL / DAT_FILESYSTEM / MSG_CHANGEDIRCTORY.

Supported Capabilities

Applications are encouraged to use this call to get the capabilities supported by a Source, since this information can be used to quickly characterize the device. For instance, a Source that supports ICAP_FLASH2 is more likely to be a digital camera than a scanner. Or in another case, a single-pass duplex scanner that supports DAT_FILESYSTEM access to both of its cameras might not support all the same capabilities for both cameras.

Extended Capabilities

This is an appropriate time to negotiate the extended capabilities CAP_EXTENDEDCAPS as indicated by CAP_SUPPORTEDEXTCAPS (ones that are settable in state 6), though there is no implied dependency in locating it here.

Feeder Control

CAP_FEEDERENABLED is the key capability to determine if a Source supports an automatic document feeder (ADF). Once this value has been determined no special ordering is required to test most of the other values, although there are groupings worth noting. Some ADFs provide control over individual sheets of paper: CAP_CLEARPAGE, CAP_FEEDPAGE, CAP_REWINDPAGE. Some ADFs are supported by memory buffers built into the device: CAP_AUTOSCAN, CAP_MAXBATCHBUFFERS. Some ADFs are capable of detecting the presence of paper in the input bin: CAP_PAPERDETECTABLE, CAP_FEEDERLOADED. ICAP_FEEDERTYPE reports either the types of feeders available (in the case where there is a general type feeder only) or the scan types supported through the feeder

Frame Management

Before negotiating frame information an Application should first establish the unit of measurement using ICAP_UNITS. It should establish the ICAP_XRESOLUTION and


Chapter A

ICAP_YRESOLUTION of the image, especially if TWUN_PIXEL is supported, since the reported values should vary with the pixel density. After that the Application should determine the physical limits of the Source using ICAP_MINIMUMHEIGHT, ICAP_MINIMUMWIDTH, ICAP_PHYSICALHEIGHT and ICAP_PHYSICALWIDTH.

Note: ICAP_MINIMUMHEIGHT, ICAP_MINIMUMWIDTH, ICAP_PHYSICALHEIGHT, and ICAP_PHYSICALWIDTH may vary depending on the source of the document. For example, when using a Flatbed / ADF combination scanner, the ADF path may permit longer documents to be scanned. In this case, values for these extents would be expected to differ for different values of CAP_FEEDERENABLED.

DAT_IMAGELAYOUT is required by all Sources. Most scanners support ICAP_SUPPORTEDSIZES (unlike digital cameras, which tend to not support physical measurements like inches and centimeters).

ICAP_SUPPORTEDSIZES is required to set itself to TWSS_NONE if frames are negotiated using either DAT_IMAGELAYOUT or ICAP_FRAMES.

ICAP_MAXFRAMES will report how many frames ICAP_FRAMES is capable of delivering per captured item.

ICAP_ORIENTATION is intended to tell a Source how the orientation of a sheet of paper fed into the scanner varies from the settings of its frame information. ICAP_ROTATION is a specific request to the scanner to rotate the scanned image the indicated number of degrees. In neither case should these capabilities affect anything but the output from DAT_IMAGEINFO. The reason for negotiating these values after establishing the frame is that some Sources may reject attempts to rotate data if one of the dimensions exceeds the physical width or height of the scanner.

ICAP_OVERSCAN is intended as a way to capture image data beyond the usual boundaries of a scanned sheet of paper, and is primarily intended as an aid in deskewing images. The additional scan area is only reported with DAT_IMAGEINFO. The reason for negotiating this value after setting the other values listed above is that some Sources may reject overscan if certain dimensions are exceeded.

ICAP_AUTOMATICDESKEW will correct the rotation of an image, it may also affect the dimensions of the image as reported by DAT_IMAGEINFO. ICAP_AUTOMATICBORDERDETECTION reduces or removes the border generated around an image by the scanner scanning its own platen (the area not covered by the paper).

ICAP_UNDEFINEDIMAGESIZE may be set to TRUE by a Source depending on one or more of the previously negotiated capabilities. Applications need to remember that it is possible for images to exceed the width and height dimensions, which can impact the amount of allocated memory. It is also important to note that if the width is undefined and ICAP_XFERMECH is set to TWSX_MEMORY, then the Source is required to also set ICAP_TILES to TRUE.

Bar Code Negotiation

ICAP_BARCODEDETECTIONENABLED must be set before any of the other, related capabilities are made available. ICAP_SUPPORTEDBARCODETYPES should then be tested, to determine what bar-code values are supported by the Source. After that the bar-code capabilities may be negotiated in any order.


Patch Code Negotiation

ICAP_PATCHCODEDETECTIONENABLED must b set before any of the other, related capabilities are made available. ICAP_SUPPORTEDPATCHCODETYPES should then be tested, to determine what patch-code values are supported by the Source. After that the patch-code capabilities may be negotiated in any order.

Imprinter/Endorser Negotiation

CAP_PRINTER establishes what (if any) printer/endorsers are supported by the Source. Selecting one establishes a context for that printer/endorser that is used by all related capabilities. CAP_PRINTERENABLED turns the printer on or off; the printer must be on in order for the other settings to be negotiated. A Source may opt to refuse to enable a printer if ICAP_SUPPORTEDSIZES selects a document with a size that is not within the area of the printer.

CAP_PRINTERINDEX should be negotiated next. CAP_PRINTERMODE can then be determined, followed by CAP_PRINTERSTRING and CAP_PRINTERSUFFIX.

Scaling

ICAP_XSCALING should be negotiated before the ICAP_YSCALING.

General Capability Negotiation

ICAP_XFERMECH selects the way an image is transferred from the Source to an Application, which has an impact on some of the characteristics of an image, which is why this value must be selected first. If TWSX_NATIVE is selected, then no other action related to image transfer is needed. If TWSX_FILE or TWSX_FILE2 is selected, then the application should negotiate ICAP_IMAGEFILEFORMAT, which will be used when DAT_SETUPFILEXFER is called. If TWSX_MEMORY is selected, then DAT_SETUPMEMXFER will need to be called. The Application may then opt to negotiate ICAP_TILES.

// Then negotiate these capabilities…

ICAP_PIXELTYPE

or

ICAP_JPEGPIXELTYPE

// Use of flash may affect other values…

ICAP_FLASHUSED

ICAP_FLASHUSED2

ICAP_AUTOBRIGHT

ICAP_BRIGHTNESS

ICAP_BITDEPTH


ICAP_CUSTHALFTONE

ICAP_HALFTONES

ICAP_THRESHOLD


Chapter A

ICAP_BITORDER

ICAP_COMPRESSION

ICAP_BITORDERCODES

ICAP_CCITTKFACTOR

ICAP_PIXELFLAVORCODES

ICAP_TIMEFILL

ICAP_CONTRAST

ICAP_EXPOSURETIME

ICAP_FILTER

ICAP_GAMMA

ICAP_IMAGEFILTER

ICAP_NOISEFILTER

ICAP_PIXELFLAVOR

ICAP_HIGHLIGHT

ICAP_SHADOW

ICAP_PLANARCHUNKY

ICAP_XRESOLUTION

ICAP_XNATIVERESOLUTION

ICAP_YRESOLUTION

ICAP_YNATIVERESOLUTION

Audio Negotiation

The availability of the audio capabilities can be inferred from the presence of DG_AUDIO. If it is available then the Application should negotiate ACAP_XFERMECH. Note that these operations occur independently of the current value of DAT_XFERGROUP. The actual selection of an audio file format takes place in State 6 using DAT_SETUPFILEXFER, and must be preceded by a call to DAT_XFERGROUP / MSG_SET to DG_AUDIO to change the Source over to the audio data group. Sources that transfer audio data need to set the Source back to DG_IMAGE when they are done with the audio data, and ready to get image data, or exit back to State 4.

Alarms

CAP_ALARMS selects the kind of audio alerts provided by a Source. CAP_ALARMVOLUME is only available if an alarm is selected, and controls the volume for all alarms with a single value.

Power Supply

CAP_POWERSUPPLY reports which power supply is currently in effect for the Source. CAP_BATTERYPERCENTAGE, CAP_BATTERYMINUTES and CAP_POWERDOWNTIME are available at all times, though the values they report may change depending on the current value of CAP_POWERSUPPLY.


Asynchronous Device Events

CAP_DEVICEEVENT may be used to activate device events.

Automatic Capture

DG_CONTROL / DAT_FILESYSTEM / MSG_AUTOMATICCAPTUREDIREDCTORY should be negotiated first, since it selects the destination for the images. CAP_TIMEBEFOREFIRSTCAPTURE and CAP_TIMEBETWEENCAPTURES should be negotiated next. CAP_AUTOMATICCAPTURE must be negotiated last, because it is the trigger that starts the timer.

Camera-Dependent Capabilities

The following list covers capabilities have no interdependencies, but which may be dependent on the currently selected device (for Sources that support DAT_FILESYSTEM).

CAP_AUTHOR

CAP_CAMERASIDE

CAP_CAPTION

CAP_DEVICETIMEDATE

CAP_ENDORSER

CAP_JOBCONTROL

CAP_PASSTHRU

CAP_SERIALNUMBER

CAP_TIMEDATE

CAP_XFERCOUNT

ICAP_EXTIMAGEINFO

ICAP_IMAGEDATASET

ICAP_LAMPSTATE

ICAP_LIGHTPATH

ICAP_LIGHTSOURCE

ICAP_ZOOMFACTOR

Camera-Independent Capabilities

The following list covers capabilities that are free of any dependencies. Applications can negotiate these in any order (during state 4), and regardless of the current device in effect (for Sources that support DAT_FILESYSTEM):

CAP_CAMERAPREVIEWUI

CAP_CUSTOMDSDATA

CAP_DEVICEONLINE

CAP_DEVICETIMEDATE


Chapter A

CAP_ENABLEDSUIONLY

CAP_INDICATORS

CAP_PASSTHRU

CAP_SEGMENTED

CAP_THUMBNAILSENABLED

CAP_TIMEDATE

CAP_UICONTROLLABLE

CAP_XFERCOUNT

DefaultsTWAIN describes defaults for capabilities, unfortunately, this information is spread throughout the specification, and in some cases is ambiguous. This article discusses how Sources and Applications should use and manage defaults values. It covers the three main kinds of defaults supported by TWAIN. It discusses the DG_CONTROL / DAT_CAPABILITY / MSG_xxxx functions and how they relate to defaults. Finally, it offers a section that describes the expected default settings for each capability within TWAIN.

Default Mechanisms

Defaults in TWAIN serve three main functions:

Mandatory Defaults Protect Applications from incompatible settings.

Preferred Defaults Permit Source providers to expose preferred settings for capabilities.

User Defaults Create consistency in a Source’s user interface; values selected in one session are preserved for the next session.

Mandatory defaults are established by the TWAIN specification. Preferred defaults may be selected by a Source for any capability that does not have a mandatory default. User defaults may replace any preferred default with a value selected by the user through the Source’s user interface. These three functions are not intrinsically compatible, which creates ambiguity; Applications cannot make assumptions about the initial values of all capabilities.

Mandatory Defaults

Some capabilities must reflect certain values when a Source is opened. These defaults are selected because Applications must be allowed to expect certain kinds of behavior without being forced to negotiate all capabilities (not only would this be tedious, but it is impossible in situations where a Source and Application are derived from different versions of TWAIN). For example, the 1.8 capability CAP_PRINTERENABLED must default to FALSE, otherwise a 1.6 Application might find itself printing data on scanned documents, and unable to do anything about it.


Preferred Defaults

TWAIN permits a Source to provide its own defaults. These settings are assumed to produce the most favorable results possible, whether they are measured in terms of processing speed, memory usage, or some other criteria. For instance, a Source will select a preferred value for ICAP_PIXELFLAVOR that keeps it from having to invert the bits in an image. In some cases the preferred defaults are gleaned from the current state of the device. For instance, CAP_FEEDERENABLED depends on the presence of a feeder on the scanner device. A Source is expected to determine if the feeder is truly present, not assume that the value saved from the last session is valid.

User Defaults

Prior to TWAIN 1.7 Applications generally relied on Sources to provide user interfaces that controlled image capture. Since one of the tenants of TWAIN is to make things easier for Applications, it became common for Sources to save state, preserving the values selected by a user, so the next time the Application started the same values would be displayed. This mechanism continues to be desirable, but Source writers should bear in mind that user defaults values are a convenience that can create problems for users who access their Source from more than one Application. CAP_AUTOSCAN is an example of a capability that should never have its state saved, since Applications that do not negotiate will also not be able to handle the results if it happens to be set to TRUE.

DAT_CAPABILITY Operations

There are five methods of negotiating values with a Source, this section discusses how Sources and Applications should relate them to the various kinds of default values:

• MSG_GET returns the current value of the capability, along with the allowed values (if any). At startup, this value will reflect the mandatory default, if there is one. If there is no mandatory default, then this call will return the user default, if supported and if one is available; otherwise it will return the preferred default value for the Source. It is up to the Application to understand the possible sources of a value, and override it if desired. Note that the allowed values are always reset when a Source starts up. Sources must never save the constraints created by an Application.

• MSG_GETCURRENT returns the current value of the capability, it does not return the allowed list. At startup, this value will reflect the mandatory default, if there is one. If there is no mandatory default, then this call will return the user default, if supported and if one is available; otherwise it will return the preferred default value for the Source.

• MSG_GETDEFAULT always returns either the mandatory or preferred default, whichever is appropriate for the capability. It never returns a user default. Like MSG_GETCURRENT it only returns the value, not the allowed list.

• MSG_RESET resets a capability’s allowed list to all permitted values, and sets the current value to the mandatory or preferred default, never the user default. The container returned by MSG_RESET must be the same kind of container returned for a MSG_GETDEFAULT operation, this preserves legacy behavior; however, Applications should follow MSG_RESET with MSG_GET if they wish to determine how the constraints for the capability have been reset. This message is a good one for Applications to use, since it is easy to code, and can be used to get a Source to some kind of a known state.

A simple mechanism for resetting a Source uses the following steps (Applications that use the Source’s UI should not use this method): for each device supported by the Source (pre-1.8 Sources


Chapter A

only have one implicit device) the Application calls CAP_SUPPORTEDCAPS; for each capability the Application calls DG_CONTROL / DAT_CAPABILITY / MSG_QUERYINTERFACE to see if it supports TWQI_RESET; if it does, then the Application sends DG_CONTROL / DAT_CAPABILITY / MSG_RESET which resets the capability.

Performing these steps will protect an Application from any user defaults created by a previous Application. Please note, not all Sources may support MSG_QUERYINTERFACE. For those that don’t, an Application would have to issue MSG_RESET on all capabilities (perhaps excluding those it knows to be read-only) and trust that the Source is robust enough to report TWRC_FAILURE for those capabilities that do not support MSG_RESET.

• MSG_SET sets the current value and optionally sets the constraints on a capability. Sources must never save the constrains negotiated by an Application. The case of the current value is a little different, since a Source is supposed to reflect the negotiated values in its UI, it’s possible for a capability set in State 4 to find its way into the user defaults.

Capability Default-Values Table

This table details for each capability whether its defaults are mandatory or not (preferred and user defaults are non-mandatory), along with the default value, if any. Note that some capabilities do not support defaults (actions), or have defaults that are governed by the current device, or have defaults that are always equal to the current value (read-only values). It is worth reiterating that the use of the word Mandatory does not imply that the capability must be present in a Source, only that if it is present its initial value is defined by this specification.

Capability Type Value / Comments

ACAP_XFERMECH Mandatory TWSX_NATIVE

CAP_ALARMVOLUME Preferred / User No default

CAP_ALARMS Preferred / User No default

CAP_AUTHOR Preferred / User No default

CAP_AUTODISCARDBLANKPAPER Mandatory FALSE

CAP_AUTOFEED Preferred / User No default

CAP_AUTOMATICCAPTURE Preferred / User No default. It is possible for an Application to disconnect from a device, leaving it in a state where it will automatically take pictures at the specified time. This value is preserved so that after a disconnect, a reconnect will not reset automatic capture and prevent the device from taking pictures.

CAP_AUTOSCAN Mandatory FALSE

CAP_BATTERYMINUTES n/a Read-only value

CAP_BATTERYPERCENTAGE n/a Read-only value

CAP_CAMERAPREVIEWUI n/a Read-only value


CAP_CAMERASIDE n/a TWCS_BOTH

CAP_CAPTION Preferred / User No default

CAP_CLEARBUFFERS Mandatory TWCB_AUTO

CAP_CLEARPAGE n/a n/a

CAP_CUSTOMDSDATA n/a Read-only value

CAP_DEVICEEVENT Mandatory Empty, no events reported by MSG_GET

CAP_DEVICEONLINE n/a Read-only value

CAP_DEVICETIMEDATE n/a Device generated value

CAP_DUPLEX n/a Read-only value

CAP_DUPLEXENABLED Preferred / User Read-only value

CAP_ENABLEDSUIONLY n/a Read-only value

CAP_ENDORSER Mandatory 0

CAP_EXTENDEDCAPS Mandatory Empty, no capabilities reported by MSG_GET

CAP_FEEDERALIGNMENT n/a Read-only value

CAP_FEEDERENABLED Preferred / User No default

CAP_FEEDERLOADED n/a Read-only value

CAP_FEEDERORDER n/a Read-only value

CAP_FEEDPAGE n/a Device action

CAP_INDICATORS Mandatory TRUE

CAP_JOBCONTROL Mandatory TWJC_NONE

CAP_LANGUAGE Preferred / User In the following order:appIdentity->Version.LanguageGetLocaleInfo(LOCALE_USER_DEFAULT)Preferred (some suitable secondary language, such as English or French)

CAP_MAXBATCHBUFFERS n/a Calculated value

CAP_PAGEMULTIPLEACQUIRE n/a Read-only value

CAP_PAPERDETECTABLE n/a Read-only value

CAP_POWERSAVETIME Preferred / User No default

CAP_POWERSUPPLY n/a Read-only value

CAP_PRINTER n/a No default



Chapter A

CAP_PRINTERENABLED Mandatory FALSE (for each item in CAP_PRINTER)

CAP_PRINTERINDEX Preferred / User No default

CAP_PRINTERMODE Preferred / User No default

CAP_PRINTERSTRING Preferred / User No default

CAP_PRINTERSUFFIX Preferred / User No default

CAP_REWINDPAGE n/a Device action ???Read-only value

CAP_SEGMENTED Preferred / User TWSG_None

CAP_SERIALNUMBER n/a Read-only value

CAP_SUPPORTEDCAPS n/a Read-only value

CAP_TIMEBEFOREFIRSTCAPTURE Preferred / User No default

CAP_TIMEBETWEENCAPTURES Preferred / User No default

CAP_TIMEDATE n/a Read-only value

CAP_THUMBNAILSENABLED Mandatory FALSE

CAP_UICONTROLLABLE n/a Read-only value

CAP_XFERCOUNT Mandatory -1

ICAP_AUTOMATICBORDERDETECTION Mandatory FALSE

ICAP_AUTOBRIGHT Preferred / User No default

ICAP_AUTOMATICDESKEW Mandatory FALSE

ICAP_AUTOMATICROTATE Mandatory FALSE

ICAP_BARCODEDETECTIONENABLED Mandatory FALSE

ICAP_BARCODEMAXRETRIES Preferred / User No default

ICAP_BARCODEMAXSEARCHPRIORITIES Preferred / User No default

ICAP_BARCODESEARCHMODE Preferred / User No default

ICAP_BARCODESEARCHPRIORITIES Preferred / User No default

ICAP_BARCODETIMEOUT Preferred / User No default

ICAP_BITDEPTH Preferred / User No default

ICAP_BITDEPTHREDUCTION Preferred / User No default

ICAP_BITORDER Preferred / User No default

ICAP_BITORDERCODES Preferred / User No default

ICAP_BRIGHTNESS Preferred / User No default

ICAP_CCITTFACTOR Preferred / User No default

ICAP_COMPRESSION Mandatory TWCP_NONE



ICAP_CONTRAST Preferred / User No default

ICAP_CUSTHALFTONE Preferred / User No default

ICAP_EXPOSURETIME Preferred / User No default

ICAP_EXTIMAGEINFO Mandatory FALSE

ICAP_FEEDERTYPE Preferred / User TWFP_GENERAL

ICAP_FILTER Mandatory TWFT_NONE

ICAP_FLASHUSED Preferred / User Preferred or Device controlled default

ICAP_FLASHUSED2 Preferred / User Preferred or Device controlled default

ICAP_FLIPROTATION Mandatory TWFR_BOOK

ICAP_FRAMES Preferred / User No default

ICAP_GAMMA Preferred / User No default

ICAP_HALFTONES Preferred / User No default

ICAP_HIGHLIGHT Preferred / User No default

ICAP_IMAGEDATASET Mandatory Default to entire range of images

ICAP_IMAGEFILEFORMAT Preferred / User No default TWFF_BMP (Windows)TWFF_PICT (Macintosh)

ICAP_IMAGEFILTER Preferred / User No default

ICAP_JPEGPIXELTYPE Preferred / User No default

ICAP_LAMPSTATE Preferred / User No default

ICAP_LIGHTPATH Preferred / User No default

ICAP_LIGHTSOURCE Preferred / User No default

ICAP_MAXFRAMES Preferred / User No default

ICAP_MINIMUMHEIGHT n/a Read-only value

ICAP_MINIMUMWIDTH n/a Read-only value

ICAP_NOISEFILTER Preferred / User No default

ICAP_ORIENTATION Mandatory TWOR_PORTRAIT

ICAP_OVERSCAN Mandatory TWOV_NONE

ICAP_PATCHCODEDETECTIONENABLED Mandatory FALSE

ICAP_PATCHCODEMAXRETRIES Preferred / User No default

ICAP_PATCHCODEMAXSEARCHPRIORITIES

Preferred / User No default

ICAP_PATCHCODESEARCHMODE Preferred / User No default

ICAP_PATCHCODESEARCHPRIORITIES Preferred / User No default



Chapter A

ICAP_PATCHCODETIMEOUT Preferred / User No default

ICAP_PHYSICALHEIGHT n/a Read-only value

ICAP_PHYSICALWIDTH n/a Read-only value

ICAP_PIXELFLAVOR Preferred / User No default. This is a break from previous versions of TWAIN, made to better support the potential difference in pixel flavor between bitonal and grayscale data in the same device (note that pixel flavor is not defined to have any meaning for color data). Sources are encouraged to default to TWPF_CHOCOLATE if they are accessed by an Application using a protocol prior to TWAIN 1.9. Applications are strongly encouraged to check an image’s pixel flavor in state 7, at least once per batch.

ICAP_PIXELFLAVORCODES Preferred / User No default

ICAP_PIXELTYPE Preferred / User No default

ICAP_PLANARCHUNKY Preferred / User No default

ICAP_ROTATION Mandatory 0

ICAP_SHADOW Preferred / User No default

ICAP_SUPPORTEDBARCODETYPES n/a Read-only value

ICAP_SUPPORTEDPATCHCODETYPES n/a Read-only value

ICAP_SUPPORTEDSIZES Preferred / User No default

ICAP_THRESHOLD Preferred / User No default

ICAP_TILES Mandatory FALSE

ICAP_TIMEFILL Preferred / User No default

ICAP_UNDEFINEDIMAGESIZE Mandatory FALSE

ICAP_UNITS Preferred / User TWUN_INCHES

ICAP_XFERMECH Mandatory TWSX_NATIVE

ICAP_XNATIVERESOLUTION n/a Read-only value

ICAP_XRESOLUTION Preferred / User No default

ICAP_XSCALING Preferred / User No default

ICAP_YNATIVERESOLUTION n/a Read-only value

ICAP_YRESOLUTION Preferred / User No default

ICAP_YSCALING Preferred / User No default

ICAP_ZOOMFACTOR Preferred / User No default



BTWAIN Technical Support

Chapter ContentsE-Mail Support . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-1Worldwide Web. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . B-2

E-Mail SupportDevelopers who are connected to AppleLink and the WWW or Internet have access to TWAIN support groups. The support groups can answer your TWAIN development or marketing questions. There are two support groups: the TWAIN Working Group and the TWAIN Developers distribution.

• The TWAIN Working Group is read by Technical, Marketing and Support representatives from the Working Group companies. You can contact this group via e-mail at [email protected].

• The TWAIN Developers distribution includes TWAIN developers who want to keep up on TWAIN or offer advice to other developers. This distribution includes the TWAIN Working Group. It is the best place to get support because both the Working Group and other developers can respond. You can contact this group via e-mail at [email protected]. In order to send mail to the list, you must first subscribe to the list at http:/email.sparklist.com/scripts/lyris.pl?enter=twain.

• For Apple-specific questions, please email the TWAIN Working Group Mac Subcommittee at [email protected].

TWAIN developers are encouraged to participate on the TWAIN Developer distribution list. The TWAIN Working Group also uses this distribution as a means to communicate with developers. For example, we use the distribution when posting the latest news about TWAIN, asking questions we may have about implementations, and requesting review of any Technical Notes that are under development. Technical Notes provide the mechanism for distributing updated information and corrections to errors that may occur in this document.

TWAIN 2.1 Specification B-1

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[email protected]

http://email.sparklist.com/scripts/lyris.pl?enter=twain

http://email.sparklist.com/scripts/lyris.pl?enter=twain

[email protected]

Chapter B

Worldwide WebDevelopers connected to the WWW can also get on-line information and updates. There is an on-line version of the Developers’ matrix with connections to those implementers with WWW pages. In addition, this manual is available as a readable file.

The WWW address is http://www.twain.org/

B-2 TWAIN 2.1 Specification

Twain 2 1 Spec

Documents

twain session

elements of twain

acknowledgmentsthe twain

twain specificationversion

twain architecture

twain user interface

data types

data structures